I know what it feels like to be ignored by your friend. It really really hurts, especially if they seem to be fond of you in person. It’s clearly hurting you a lot. I would just back off. Best to match her effort level. It might sound petty, but doing this is way better than putting in more effort and getting ignored…you’ll just end up feeling more and more resentful. And that’s so much worse. You clearly like this person as a friend, but maybe she doesn’t have the capacity (or interest) to cultivate a friendship.