היא נורא שמחה שהמורה נתנה לה תשובה כנה ולא ניסתה לשנות את הנושא.

Because the subject is היא (she), and adjectives in Hebrew agree with the noun or pronoun they describe in gender and number.

• שמח = masculine singular
• שמחה = feminine singular
• שמחים = masculine plural
• שמחות = feminine plural

So היא נורא שמחה means she was very happy.

Yes, literally נורא can mean terrible, awful, or dreadful in some contexts. But in everyday spoken Hebrew, it is also very commonly used as an intensifier meaning very, really, or super.

So here:

• נורא שמחה = very happy / really happy

This is a very common colloquial use.

Both ש־ and כי can sometimes be translated as that, but they are not used exactly the same way.

In this sentence, ש־ is the normal, natural choice for introducing a subordinate clause in everyday Hebrew:

• היא שמחה שהמורה נתנה לה תשובה כנה
  = She was happy that the teacher gave her an honest answer

Using כי here would sound more formal, literary, or sometimes less natural in everyday speech.

So for spoken modern Hebrew, ש־ is the expected form.

Because the subject המורה is understood here as female.

Hebrew past-tense verbs agree with the subject in gender and number:

• נתן = he gave
• נתנה = she gave
• ניסה = he tried
• ניסתה = she tried

So:

• המורה נתנה = the teacher gave (female teacher)
• ולא ניסתה = and did not try (same female teacher)

Also, מורה itself can refer to either a male or female teacher. The verb form tells you which one is meant here.

לה means to her.

The verb לתת (to give) often takes:

• a giver
• something given
• a recipient

So in:

• המורה נתנה לה תשובה כנה

the parts are:

• המורה = the teacher
• נתנה = gave
• לה = to her
• תשובה כנה = an honest answer

So literally: the teacher gave to her an honest answer.

Hebrew does not have an indefinite article like English a/an.

So:

• תשובה can mean an answer or answer
• תשובה כנה = an honest answer

If Hebrew wants to say the answer, it uses the definite article ה־:

• התשובה הכנה = the honest answer

So the absence of ה־ usually gives the indefinite meaning.

In Hebrew, adjectives usually come after the noun, unlike in English.

So:

• תשובה כנה = literally answer honest
• natural English: an honest answer

Also, the adjective must agree with the noun:

• תשובה is feminine singular
• so the adjective is כנה (feminine singular)

Compare:

• ספר טוב = a good book (masculine)
• תשובה טובה = a good answer (feminine)

Hebrew often leaves out subject pronouns when the subject is clear from the verb form or context.

Here, after שהמורה נתנה לה תשובה כנה, it is already clear that המורה is still the subject. So Hebrew naturally continues with:

• ולא ניסתה לשנות את הנושא
  = and did not try to change the subject

Adding והיא or repeating המורה is possible in some contexts, but it is not necessary here and would usually sound less smooth.

This is a very common Hebrew pattern:

• conjugated verb + infinitive with ל־

Here:

• ניסתה = she tried
• לשנות = to change

So:

• ניסתה לשנות = she tried to change

This works like English tried to do.

Other examples:

• רצתה ללכת = she wanted to go
• התחיל לדבר = he began to speak
• הפסיק לעבוד = he stopped working

את marks a definite direct object.

So in:

• לשנות את הנושא = to change the subject

the object is הנושא (the subject/topic), and because it is definite, Hebrew uses את before it.

Compare:

• לשנות נושא = to change a topic / change topics
• לשנות את הנושא = to change the topic / change the subject

A very important point: את does not mean with here. It is just an object marker.

It can mean both, depending on context.

Here, in the phrase:

• לשנות את הנושא

it means to change the subject, in the conversational sense of changing the topic.

That is a fixed and very common expression in Hebrew.

The sentence has one main clause and then a subordinate clause introduced by ש־.

Breakdown:

• היא נורא שמחה
  = She was very happy

• שהמורה נתנה לה תשובה כנה
  = that the teacher gave her an honest answer

• ולא ניסתה לשנות את הנושא
  = and did not try to change the subject

So the whole sentence is:

• She was very happy that the teacher gave her an honest answer and didn’t try to change the subject.

Yes. מורה is one of those nouns that can refer to either a male or female person.

So:

• המורה נתן שיעורי בית = the teacher gave homework (male)
• המורה נתנה שיעורי בית = the teacher gave homework (female)

In your sentence, the feminine verbs נתנה and ניסתה show that the teacher is female.

Yes, usually.

Both can mean very happy:

• נורא שמחה = more colloquial, everyday, spoken
• מאוד שמחה = neutral, standard, very common in both speech and writing

So the sentence could also be:

• היא מאוד שמחה שהמורה נתנה לה תשובה כנה...

That would still sound natural, just a little less colloquial in tone.

Yes, that is the natural implication.

If someone doesn’t try to change the subject, it suggests they are being direct and not avoiding the issue. So together with תשובה כנה (an honest answer), the sentence gives a strong feeling that the teacher responded openly and sincerely.

So the second part supports the first:

• תשובה כנה = honest answer
• ולא ניסתה לשנות את הנושא = she didn’t try to dodge the issue

Yes, that is the most natural reading.

The grammar suggests:

• היא = a female person
• המורה נתנה... ולא ניסתה... = the teacher is also female

So the sentence most naturally refers to a woman/girl who was happy that her female teacher gave her an honest answer and didn’t try to change the subject.

If the teacher were male, the verbs would be masculine:

• שהמורה נתן לה תשובה כנה ולא ניסה לשנות את הנושא