Эта певица поёт так уверенно, что я не могу не слушать её очень внимательно.

Because певица is a feminine singular noun, and the demonstrative this must agree with it in gender, number, and case.

• этот = masculine singular
• эта = feminine singular
• это = neuter singular
• эти = plural

So:

• эта певица = this singer
  because певица is feminine.

Also, певица is in the nominative case here, since it is the subject of the sentence.

Yes. Певица means female singer.

Russian often has separate masculine and feminine nouns for professions or roles:

• певец = male singer
• певица = female singer

Since the sentence uses эта and поёт, we know the subject is a woman: this female singer.

Петь is the dictionary form (the infinitive), meaning to sing.
Поёт is the 3rd person singular present tense form, meaning:

• she sings
• she is singing

So:

• петь = to sing
• она поёт = she sings / she is singing

Here the subject is эта певица, so the verb must be in the form that matches she:

• Эта певица поёт = This singer sings / is singing

A useful note: поёт is often written as поет in casual texts, but the pronunciation is really поёт with ё.

Because уверенно is an adverb, and it describes how she sings.

• уверенный / уверенная = confident (adjective, describes a noun)
• уверенно = confidently (adverb, describes a verb)

In this sentence, we are not describing the singer as confident directly. We are describing the way she sings:

• Она уверенная = She is confident
• Она поёт уверенно = She sings confidently

So уверенно is correct because it modifies поёт.

Так ..., что ... is a very common Russian structure meaning so ... that ...

In your sentence:

• так уверенно = so confidently
• что = that

So the pattern is:

• Она поёт так уверенно, что...
• She sings so confidently that...

This structure is used a lot:

• Он говорит так быстро, что я ничего не понимаю.
  = He speaks so quickly that I understand nothing.
• Было так холодно, что мы не вышли.
  = It was so cold that we didn’t go out.

This is a very common and important Russian pattern.

• не могу = I cannot
• не слушать = not listen

Together, не могу не слушать literally looks like I cannot not listen, but the natural meaning is:

• I can’t help listening
• I can’t help but listen

So the double negative here is not a mistake. It is an idiomatic structure meaning that something is so compelling that the speaker is unable to resist doing it.

Similar examples:

• Я не могу не улыбаться.
  = I can’t help smiling.
• Он не мог не согласиться.
  = He couldn’t help agreeing.

Because слушать means to listen (to), while слышать means to hear.

This is a very important distinction:

• слышать = to hear, to perceive sound
• слушать = to listen, to pay attention to sound

In this sentence, the speaker is actively paying attention to the singer, so слушать is the correct verb.

Compare:

• Я слышу музыку. = I hear music.
• Я слушаю музыку. = I am listening to music.

Since the sentence also says очень внимательно (very attentively), that strongly fits слушать, not слышать.

Because её is the correct form of она when it is the direct object of the verb.

The basic pronoun forms are:

• она = she
• её = her

So:

• Она поёт. = She sings.
• Я слушаю её. = I listen to her.

Here, её is in the accusative case, because слушать takes a direct object.

A small detail: for feminine animate pronouns, the accusative form is её, which looks the same as the genitive form. But in this sentence its role is accusative because it is the object of слушать.

Russian word order is more flexible than English word order, because case endings do a lot of the grammatical work.
So yes, the word order could be changed, but the emphasis would shift.

In the given sentence:

• ...слушать её очень внимательно
• ...listen to her very attentively

This sounds natural and neutral.

You could also say:

• ...очень внимательно слушать её
• ...слушать очень внимательно её (less neutral, more marked)

The original version puts the adverb phrase near the end, which is quite natural and gives a smooth flow.

So the main idea is:

• the meaning stays similar
• the emphasis and style can change

Певица is in the nominative singular.

Why?

Because it is the subject of the sentence — the person performing the action:

• Эта певица поёт...
• This singer sings...

The subject of a normal statement is usually in the nominative case.

Поёт comes from петь, which is an imperfective verb.

That matters because the sentence is describing an ongoing or general action:

• she sings
• she is singing

The imperfective aspect is used for:

• ongoing actions
• repeated actions
• general descriptions

This sentence is not about completing one song. It is about the manner of her singing, so the imperfective is exactly what you would expect.

Yes. That is a very natural English translation.

The key part is:

• не могу не слушать её = I can’t help listening to her / I can’t help but listen to her

And:

• очень внимательно = very attentively / very carefully

So natural English versions include:

• This singer sings so confidently that I can’t help listening to her very carefully.
• This singer sings so confidently that I can’t help but listen to her very attentively.

The exact English wording can vary, but the Russian structure stays the same.

Not always, but here it does.

Её can mean:

• her as an object
  
  • Я вижу её. = I see her.
• her / hers in a possessive sense
  
  • её книга = her book

In your sentence, её comes after the verb слушать, so it is clearly the object:

• слушать её = listen to her

So here it definitely means her, not her book or anything possessive.

Because Russian handles this differently.

In English, listen normally needs the preposition to:

• listen to her

In Russian, слушать takes a direct object without a preposition:

• слушать её

So you should think of слушать as behaving more like a transitive verb in Russian.

This is something learners just need to memorize:

• слушать музыку = to listen to music
• слушать учителя = to listen to the teacher
• слушать её = to listen to her

It breaks down like this:

• Эта певица = subject noun phrase
• поёт = verb
• так уверенно = adverbial phrase describing how she sings
• что = conjunction introducing the result clause
• я = subject of the second clause
• не могу не слушать её = verbal structure meaning I can’t help listening to her
• очень внимательно = adverbial phrase describing how I listen

So the sentence has a clear cause/result feel:

1. She sings so confidently
2. that I can’t help listening to her very attentively