היא מחייכת, וגם אני מחייך.

Because in Hebrew, the present-tense form agrees with gender and number.

• מחייכת = smiling for a singular feminine subject
• מחייך = smiling for a singular masculine subject

So:

• היא מחייכת = She is smiling
• אני מחייך = I am smiling said by a male speaker

Hebrew does this much more consistently than English, where smiling stays the same.

Because אני means I, but Hebrew still marks the speaker’s gender in the verb/adjective form in the present tense.

So:

• A man says: אני מחייך
• A woman says: אני מחייכת

English does not usually show this difference, but Hebrew does.

It would be:

היא מחייכת, וגם אני מחייכת.

Both היא and אני would take the feminine singular form מחייכת.

In Hebrew, the verb to be is usually not expressed in the present tense.

So Hebrew says:

• היא מחייכת literally: she smiling
• אני מחייך literally: I smiling

But in natural English, we translate these as:

• She is smiling
• I am smiling

This is a very common feature of Hebrew.

This is the present tense.

In modern Hebrew, the present tense is usually based on forms that historically behave a bit like participles, but for learners the most useful thing is:

• treat מחייך / מחייכת as the normal present-tense forms of לחייך (to smile)

So this sentence means something like:

• She is smiling, and I am smiling too or
• She smiles, and I smile too

Usually the context makes is smiling the best translation here.

וגם means and also, and too, or and as well.

It is made of:

• ו־ = and
• גם = also / too

So:

• וגם אני מחייך = and I’m smiling too / and I am also smiling

גם means also / too.

וגם means and also, because it includes the prefix ו־ (and).

Examples:

• אני גם מחייך = I’m also smiling
• וגם אני מחייך = And I’m smiling too

In your sentence, וגם connects the second clause to the first very naturally.

Yes. That is also a natural sentence.

Compare:

• היא מחייכת, וגם אני מחייך = She’s smiling, and I’m smiling too
• היא מחייכת, ואני גם מחייך = She’s smiling, and I’m also smiling

The meaning is very close. The difference is mainly in emphasis and rhythm:

• וגם אני puts a bit more focus on I too
• אני גם puts the also slightly later

Both are common.

The comma separates the two connected parts:

• היא מחייכת
• וגם אני מחייך

It helps show a pause, just like in English.

In informal writing, some people may omit the comma, but using it here is normal and clear.

A common pronunciation would be:

Hi me-kha-ye-khet, ve-gam a-ni me-kha-yekh.

More roughly word by word:

• היא = hi
• מחייכת = me-kha-YE-khet
• וגם = ve-GAM
• אני = a-NI
• מחייך = me-kha-YEKH

The sound written here as kh is the throaty Hebrew sound, like the ch in German Bach or Scottish loch.

That is part of how many Hebrew present-tense forms are built.

The dictionary form is לחייך (to smile), and the present-tense forms are:

• מחייך = masculine singular
• מחייכת = feminine singular
• מחייכים = masculine plural
• מחייכות = feminine plural

So the מ־ is not a separate word here; it belongs to the verb form itself.

For practical learning, treat it as the present-tense verb form: smiling / is smiling.

Grammatically, Hebrew present-tense forms often behave in ways similar to adjectives, because they agree in gender and number:

• הוא מחייך
• היא מחייכת
• הם מחייכים
• הן מחייכות

So the short answer is: in this sentence, it functions as the normal present tense of to smile.

Because Hebrew grammar requires agreement in the present tense, even for first person.

English says:

• I am smiling for both men and women

Hebrew says:

• אני מחייך if the speaker is male
• אני מחייכת if the speaker is female

This is completely normal in Hebrew and is one of the things English speakers need to get used to early on.

Yes, it sounds natural and straightforward.

It is a simple conversational sentence that a native speaker could easily say. It is neither especially formal nor especially slangy.

It works well in contexts like:

• describing what is happening right now
• reacting to someone else’s mood
• saying she’s smiling, and I am too