Learn Italian: Non portargliela! Preferisce le forbici. - Do not bring it to her! She prefers the scissors.

In the negative informal imperative (telling someone not to do something), you use non + the infinitive verb. With double pronouns like gliela, you actually have two options. You can attach them to the end of the infinitive by dropping its final -e (Non portargliela!), or you can put them before the verb (Non gliela portare!). Both are perfectly correct.

The translation says "to her", but doesn't gli usually mean "to him"?

Yes, when used alone. However, when the indirect object pronouns gli (to him) and le (to her) combine with a direct object pronoun like la (it), they both change into the exact same prefix: glie-. This means gliela can mean either "it to him" or "it to her", and you must rely on context to know which one it is.

What does the -la in portargliela refer to?

It is the direct object pronoun for "it". Because it uses the feminine singular la, we know the item you shouldn't bring is a feminine noun that was mentioned earlier in the conversation (for example, la spillatrice, the stapler).

Why is forbici used with the plural article le?

Forbici (scissors) is a feminine plural noun. Just like in English, Italian treats it as plural because the tool is made of two blades, even when you are only talking about one pair of scissors.