I'm in this exact situation right now. It's heartbreaking. Not that she's said anything specifically sexual, but her crush on me is very obvious. Disclaimer: I'm not a pedo. I'm a teacher, and this isn't even the first time this has happened, so if I was a pedo I'd probably be jailed already. Though the earlier cases were all younger. This kid is mature enough (definitely acts more mature than the rest of her class) that you can have real conversations with her. With younger kids it's a bit different. It's not heartbreaking because of my disappointment at not being able to be a pedo. It's heartbreaking because this is a really sweet kid I see every day, who is very helpful, who is very friendly, who likes to talk with me and is mature enough that we can have interesting, fun, and insightful conversations, and really get to know each other. She's a good daughterfu, and I don't have kids of my own (because legal girls all reject me, and definitely don't approach me, like this girl does). But I see her disappointment, because though she clearly has a crush on me, she knows it would be futile to openly vocalize it, though she does sometimes vocalize her disappointment at the fact that she knows what relationship we do have (a friendly teacher/student relationship, you pervs) will end eventually.
She's a slightly chubby girl who totally has the personality of someone from this site. She says she hates how tv ads act like it's bad to say people are fat (basically she hates SJWs but doesn't know they're called that), and she started taking karate classes last year to try to get fit (and has gotten pretty good, too). She's into weird shit like martial arts movies and her best friend is a legit autistic girl (who is also very sweet, but normalfags in her class all treat her like a full blown retard, which she's not). She also hates all the normalfag shit that kids her age are into, so she likes talking to me because I admit to her that I agree, and I know the older non-normalfag stuff she likes. Basically, she has just the right level of autism that I'm the only person she knows that she can share her autism with. Reminds me of myself when I was a kid.
Whenever she sees me, even if it's from far away, she runs over to me, leaving her friends behind to hug me and tell me how much she missed me since the last time she saw me, even if it was only a couple hours before. She'll then follow me around and hang out with me until I have to go somewhere else where it would be against the rules for her to follow, and even then she'll playfully grab my arm and tell me not to go.
Her friends will come over and invite her to go play, and I encourage her to join them, but she is adamant that she prefers to stay and spend time with me. If I have to walk around to do various tasks, she'll follow me to help with all of them, and if I end up in an area she doesn't want to be (like sometimes I need to go help some kids who were playing in the mud, and she doesn't want to get too dirty), she won't just go back to her friends. She will still follow me, but take the earliest opportunity to ask me to just go somewhere else with her, because she doesn't want to leave me. If I can't leave when she asks, she'll still stay with me but keep pestering me about it.
Actually, a lot of times I think her above reaction isn't because she doesn't want to be in the muddy field or whatever, but just because she wants me to herself, and doesn't like that I left where we were hanging out to go help other kids. When other kids come over to me, usually since they see her always hanging out with me and laughing, and they want to see what's so funny, she gets a bit jealous, and tries to subtly get them to go away. When they do eventually go away, she'll let out a sigh of relief and say how glad she is that we can finally get back to our conversation, even if our conversation had reached its end, and she now needs to begin reaching for new conversation topics. She'll also complain and say "I don't know why they were following you around. They don't even really like you." She'll then notice that could be seen as an insult, even though I didn't take it as one, and quickly correct herself. "I mean, they like you, but not like I like you." (Direct quote from today, but she's said similar things a few times.)