My grandmom (from my dad's side) used to say a lot of things behind my back. For me and my mom too and it was really bad.
I don't know I guess eventually you realise this is their mindset and they don't know better. Especially if they come from a closed society and haven't been outside of it , so they haven't learned how to be more careful and sensitive about people. Gossipping or badmouthing is part of their mannerisms, so it's not your fault, it's how they roll.
I have no idea about the other thing though xD I'm really bad at this lol. There is a girl in my neighborhood that works in a cafe near my house and she looks like Cara Delevingne. You know what I do? I don't visit that cafe very often now xD Kinda lame I know lol
But speaking of which, it depends on who that girl is, and what the common ground between you two is, so you can find something to start a conversation I guess.