Does she and her friends eat out together? Do they eat out? This one is tricky. Contact me for the full explanation :)

Do. It's 2 persons so you use the plural.

DO is correct - as you noticed, 'she and her friends' mean it is plural.

Do or does in a question? We use do/does or is/are as question words when we want to ask yes/no questions. We use does and is with third-person singular pronouns (he, she, it) and with singular noun forms. We use do and are with other personal pronouns (you, we they) and with plural noun forms...does is correct in this question.