You could just leave her request in your feed and forget about it. I have probably 7 people like that currently where I am just pending their request. Or you could add her, not read her posts, and forget it ever happened. Maybe she wants to reconnect? People can surprise you. Or maybe she just wants a thousand friends to show off her popularity. You could send her a message saying, no offense but I normally only accept people on my friends list I'm actually friends with, not acquaintances. I usually just accept these people and move on unless they are people I just don't know at all or ex-boyfriends. It's really not a big deal on my facebook because I don't blab about my life or personal things so I don't take it as seriously and will add an acquaintance if they request to be friends first.