Если ты не уверена, стоит ли отправлять письмо преподавательнице сейчас, лучше подождать до утра и перечитать текст спокойно.

Because уверена is the short-form feminine adjective, used when speaking to or about a woman.

• ты не уверена = you (female) are not sure
• ты не уверен = you (male) are not sure

Russian often shows gender in the past tense and in short-form adjectives like this. So this sentence is addressed to a woman.

Если means if and introduces the condition:

• Если ты не уверена... = If you are not sure...

It works much like English if. The clause after если sets up the situation, and the main clause gives the recommendation:

• лучше подождать... = it’s better to wait...

This is a very common Russian pattern for indirect yes/no questions.

• стоит ли отправлять письмо = whether it is worth sending the letter / whether one should send the letter

Here:

• стоит = literally it is worth / it makes sense
• ли marks the embedded yes/no question, similar to English whether

So:

• Если ты не уверена, стоит ли... = If you are not sure whether...

You will often see this structure:

• Я не знаю, придёт ли он. = I don’t know whether he will come.
• Она спросила, можно ли войти. = She asked whether it was possible to come in.

Стоит is the 3rd person singular present form of стоить.

In this construction, Russian uses стоит + infinitive impersonally:

• Стоит подождать. = It’s worth waiting.
• Не стоит спорить. = It’s not worth arguing.

So in your sentence:

• стоит ли отправлять письмо = whether it’s worth sending the letter

Even though no clear subject is stated, Russian naturally uses стоит in this impersonal way.

This is about verb aspect, one of the most important parts of Russian grammar.

отправлять — imperfective

Used here because the question is about the idea/action in general:

• стоит ли отправлять письмо = whether one should send the letter

After verbs like стоит, можно, нужно, хочу, the imperfective often appears when talking about an action more generally, not focusing on its completion as a single concrete result.

подождать and перечитать — perfective

These describe recommended actions as single completed steps:

• подождать до утра = wait until morning
• перечитать текст = read the text over again

Perfective is natural because the speaker recommends doing these actions once, as complete acts.

Because the verb отправлять here implies the recipient, and the recipient goes in the dative case.

Base form:

• преподавательница = female teacher / female instructor

Dative singular:

• преподавательнице = to the teacher

So:

• отправлять письмо преподавательнице = to send a letter to the teacher

This is like:

• дать другу = give to a friend
• написать маме = write to mom

Sometimes yes, but they are not exactly the same.

• учительница usually means a school teacher
• преподавательница usually means an instructor/teacher at a college, university, or course

So преподавательнице suggests a more formal educational setting, or at least a teaching role often associated with higher education or structured instruction.

Russian often leaves out an explicit equivalent of English it is in impersonal expressions.

• Лучше подождать. = It’s better to wait.

Literally, Russian just says better to wait. This is completely normal.

Other examples:

• Надо идти. = It’s necessary to go.
• Можно войти? = May I come in? / Is it possible to enter?
• Трудно понять. = It’s hard to understand.

So лучше here works as an impersonal predicate: better to...

Because the preposition до requires the genitive case.

Base form:

• утро = morning

Genitive singular:

• утра

So:

• до утра = until morning

Other examples:

• до вечера = until evening
• до дома = as far as the house / until reaching home
• до конца = until the end

Читать means to read.
Перечитать means to reread / read over again.

The prefix пере- often adds the idea of again or over.

So:

• читать текст = read the text
• перечитать текст = read the text again / review it by rereading

In this sentence, перечитать makes sense because the person has presumably already written or read the text once and should look at it again calmly before sending.

Because it describes how to reread the text.

• спокойный = calm (adjective)
• спокойно = calmly / in a calm way (adverb)

So:

• перечитать текст спокойно = reread the text calmly

Russian usually forms many adverbs from adjectives with -о:

• быстрый → быстро = quick → quickly
• медленный → медленно = slow → slowly
• спокойный → спокойно = calm → calmly

Russian word order is fairly flexible, but this order is natural and clear.

The structure is:

1. Если ты не уверена — condition
2. стоит ли отправлять письмо... — what you’re unsure about
3. лучше подождать... — recommendation

Russian often puts the broad situation first and the advice after it. The sentence flows like this:

• If you’re not sure whether..., it’s better to...

Could parts be moved around? Sometimes yes, but this version sounds smooth and standard.

Because Russian separates the если clause from the main clause with a comma.

So:

• Если ты не уверена, ... лучше подождать...

Also, the part with стоит ли отправлять письмо преподавательнице сейчас is functioning as an embedded clause attached to не уверена.

Russian punctuation is often stricter than English with subordinate clauses, so commas appear very regularly in sentences like this.

Yes, ты is normal if the speaker is addressing someone informally: a friend, classmate, younger person, or someone they know well.

If the speaker wanted to be polite or formal, they would use вы:

• Если вы не уверены, стоит ли отправлять письмо преподавательнице сейчас, лучше подождать до утра и перечитать текст спокойно.

Notice that with вы, the adjective becomes plural/formal:

• уверены

So the original sentence sounds personal and informal.

Сейчас means now / right now, and it specifically modifies the action of sending:

• стоит ли отправлять письмо преподавательнице сейчас = whether it’s worth sending the letter to the teacher now

Its position is natural because it comes near the verb phrase it belongs to. Russian often places time words flexibly, but here сейчас clearly attaches to отправлять письмо.

Yes, but the meaning would change slightly.

• нужно ли = whether it is necessary / whether one needs to
• стоит ли = whether it is worth it / whether it makes sense

So:

• нужно ли отправлять письмо asks about necessity or obligation
• стоит ли отправлять письмо asks whether sending it is a good idea

In this context, стоит ли is more natural because the issue is judgment and timing, not strict necessity.