Right. As a grammatical explanation, "she" and "I" are always used if you're referring to the subject of the sentence (or clause). As the object of a sentence (or clause), we use "her" and "me".
E.g. Ela e eu vejamos ele. She and I see him.
Ele vê ela e eu. He sees her and me.
Though most English speakers mix this up all the time in casual speak.
Obviously 'eu' can be a male or a female and this is why amigos and amigas are both suggested answers. Assuming the sentance refers to one female (ela) and one male (eu), in this situation are amigos and amigas both acceptable? Or does it have to be amigos? I.e. does the masculine word form dominate like in Spanish?