Learn Arabic (Modern Standard): استلمت البنت هدية جميلة منه. - The girl received a beautiful gift from him.

It is a combination of the preposition من (from) and the attached pronoun ـه (him). When you want to say 'from him', 'with him', or 'to him', you attach this pronoun directly to the end of the preposition.

If the girl received the gift 'from her' instead of 'from him', how would the sentence change?

The word منه (minhu) would change to منها (minha). You simply replace the masculine attached pronoun ـه (-hu) with the feminine attached pronoun ـها (-ha).

Why does the verb استلمت (received) end with a ـت?

This ـت is the past tense feminine marker. Because the subject doing the action is البنت (the girl), the verb must agree with her. If a boy had received the gift, the verb would drop the ـت and just be استلم (istalama).

Why do both هدية (gift) and جميلة (beautiful) end with the same ة letter?

In Arabic, an adjective always comes after the noun it describes and must match its gender. Since هدية is a feminine noun (ending in the feminine marker ة, called taa marbuta), the adjective جميلة must also end with a ة to match it.