אני גאה בה, כי היא מדברת עברית טוב מאוד.

Here, בה means of her in the English sense, even though it is literally the preposition ב־ attached to her.

The key point is that Hebrew says גאה ב־... for proud of .... So:

• אני גאה בה = I’m proud of her
• literally, something like I am proud in/of her

You would use אותה only with a verb that takes a direct object, for example:

• אני רואה אותה = I see her

But גאה does not take a direct object; it takes the preposition ב־.

Yes, גאה agrees with the speaker, because it is an adjective.

A useful thing to know is that in normal unpointed spelling, the masculine singular and feminine singular are both written גאה. So from spelling alone, you often cannot tell whether the speaker is male or female.

That means:

• אני גאה בה could be said by a man or by a woman
• context, pronunciation, or vowel marks would make it clear

In the plural, the difference is easier to see:

• אנחנו גאים = masculine or mixed-gender we are proud
• אנחנו גאות = feminine we are proud

In this sentence, the pronouns are important.

Hebrew often allows subject pronouns to be omitted when the verb already shows the person clearly, especially in past and future. But here:

• גאה is an adjective, not a fully conjugated verb
• מדברת shows gender and number, but not clearly person

So מדברת by itself could mean:

• I speak (if the speaker is female)
• you speak (to one female)
• she speaks

That is why היא מדברת is much clearer than just מדברת.

The same logic applies to אני גאה: the pronoun אני tells you who the subject is.

Because Hebrew present-tense forms agree with the subject in gender and number.

Since היא is feminine singular, the verb form must also be feminine singular:

• היא מדברת = she speaks
• הוא מדבר = he speaks

Other forms are:

• אני מדבר = I speak (male speaker)
• אני מדברת = I speak (female speaker)
• הם מדברים = they speak (masculine/mixed)
• הן מדברות = they speak (feminine)

Because Hebrew normally does not use את before a language name in this kind of sentence.

With לדבר and names of languages, the usual pattern is:

• לדבר עברית
• לדבר אנגלית
• לדבר ערבית

So:

• היא מדברת עברית = she speaks Hebrew

This is just the normal way to express language ability.

Also, את is mainly used before a definite direct object, and language names after לדבר usually do not behave like that in simple sentences of this kind.

Both patterns exist, but they are used a little differently.

מדברת עברית is the most natural way to say that someone knows/speaks Hebrew as a language.

• היא מדברת עברית = She speaks Hebrew

מדברת בעברית often means speaks in Hebrew, focusing more on the language being used in that moment.

• דבר בעברית = Speak in Hebrew
• הוא כתב בעברית = He wrote in Hebrew

So in your sentence, מדברת עברית is the most natural choice for general ability.

Because טוב here is not describing she and not describing Hebrew. It is describing how she speaks.

In other words, it functions like an adverb: well.

In colloquial Hebrew, adjectives in the masculine singular form are often used this way after verbs:

• הוא שר יפה = he sings beautifully
• היא רצה מהר = she runs fast
• היא מדברת טוב = she speaks well

So טוב stays in the default masculine singular form, even though היא is feminine.

That is why טובה מאוד would be wrong here.

Because טוב מאוד is very common and natural in everyday Hebrew.

Both can mean well:

• היא מדברת עברית טוב מאוד
• היא מדברת עברית היטב

But there is a difference in tone:

• טוב מאוד = more everyday, conversational
• היטב = more formal, more written, sometimes a bit bookish

So a learner will hear טוב מאוד a lot in normal speech.

מאוד means very.

In Hebrew, מאוד usually comes after the adjective or adverb it modifies:

• טוב מאוד = very well / very good
• יפה מאוד = very beautiful / very nicely
• קשה מאוד = very difficult

So:

• מדברת עברית טוב מאוד = speaks Hebrew very well

That word order is completely normal in Hebrew.

In this sentence, כי means because.

It introduces the reason:

• אני גאה בה, כי היא מדברת עברית טוב מאוד
• I’m proud of her, because she speaks Hebrew very well

A useful warning for learners: כי can also mean that in other sentences, so you have to read it from context.

For example:

• אני יודע כי... can mean I know that...
• here, after a full statement, it clearly means because

The word order here is the most neutral and natural one:

• אני גאה בה, כי היא מדברת עברית טוב מאוד

Hebrew word order is somewhat flexible, but changing it usually changes the emphasis.

For example, you could move things around for style or emphasis, but the given version is the straightforward everyday order:

• statement first
• then the reason introduced by כי

Inside the second clause, היא מדברת עברית טוב מאוד is also the normal order:

• subject
• verb
• language
• adverb phrase

So even if other versions are possible, this one is the best basic model for learners.