Puede que mi madre pruebe un batido de vainilla, aunque normalmente prefiere café.

Because puede que expresses possibility or uncertainty, and that normally triggers the subjunctive in Spanish.

So after puede que, you say:

• Puede que mi madre pruebe...

not:

• Puede que mi madre prueba...

Prueba is the present indicative, while pruebe is the present subjunctive.

Pruebe is the present subjunctive of probar.

It comes from the yo form of the present indicative:

• yo pruebo

Then you remove -o and add subjunctive endings:

• pruebe, pruebes, pruebe, probemos, probéis, prueben

Notice the stem change o → ue, which stays in most forms.

Prefiere is the present indicative form of preferir for él/ella/usted.

Preferir is a stem-changing verb:

• yo prefiero
• tú prefieres
• él/ella prefiere

The stem changes from e → ie in most present forms.

In this sentence, prefiere is used because the speaker is stating a normal, real habit: she normally prefers coffee.

Because the second part is presented as a fact:

• aunque normalmente prefiere café

The speaker is not doubting that she usually prefers coffee; they are stating it as true.

With aunque, Spanish can use:

• indicative for something factual or known
• subjunctive for something hypothetical, uncertain, or not presented as a fact

So here the indicative prefiere is the natural choice.

Both can show contrast, but they are not used in exactly the same way.

• aunque means although / even though
• pero means but

In this sentence, aunque introduces a concessive idea: she may try a vanilla shake, although she normally prefers coffee.

If you used pero, the sentence would still make sense, but it would feel a bit more like simple contrast:

• Puede que mi madre pruebe un batido de vainilla, pero normalmente prefiere café.

That is possible, but aunque is more natural for the idea of despite that.

In Spanish, after verbs like preferir, it is very common to use a noun without an article when speaking generally about a thing, food, or drink.

So:

• prefiere café = she prefers coffee, in general

This sounds natural and idiomatic.

You may also hear prefiere el café, but that can sound slightly more specific or more like coffee as a category. In many everyday cases, the version without the article is the most neutral.

De vainilla is the normal way to describe a flavor in Spanish.

So:

• batido de vainilla = vanilla milkshake / vanilla shake

This is similar to:

• helado de chocolate
• pastel de limón

Using de is the standard pattern for flavor or type here.

Here it means to try/taste a food or drink.

With food and drink, probar often means:

• to taste
• to try

So pruebe un batido de vainilla means she may have one to see what it is like, or taste it.

If you wanted to try in the sense of attempt to do something, Spanish often uses intentar or sometimes tratar de.

Yes, Spanish often drops the subject when it is clear from context.

So you could say:

• Puede que pruebe un batido de vainilla...

But then pruebe could mean he/she/you formal may try, depending on context.

Including mi madre makes the sentence clearer and more explicit. It can also add a little emphasis.

Puede que means something like:

• it may be that
• maybe
• might

It is a very common way to express possibility, and it strongly calls for the subjunctive.

You could also say:

• Quizá mi madre pruebe...
• Tal vez mi madre pruebe...

Those are also natural. The main grammar point is that puede que is a very clear subjunctive trigger.

In this kind of sentence, the comma is normal and helpful because it separates the main idea from the contrasting clause:

• Puede que mi madre pruebe un batido de vainilla, aunque normalmente prefiere café.

It makes the sentence easier to read and reflects the pause you would usually make in speech. In standard writing, this punctuation is appropriate here.