Problems with step-daughter

I'm 42, and I'm married. I have a stepdaughter, and she's a wonderful girl. We get along great. When I got married she was 10. Her father left her mom when she was 4, and she doesn't even really remember him. He doesn't call or talk to her or anything, so I guess it was nice for her to have a father figure. She snuggles up to me and treats me as though I were her father except she calls me Jorge. Anyway, I've been married for 5 years, so now she's 15. She still snuggles up to me as she always did, but now it's different. For example, last week we were snuggling on the couch and watching a sitcom. She was enjoying it, and laughing a lot, but somehow every time she laughed her body moved against me (we were spooning) and I started to like it – you know, more than I should have. So, you know, I'm embarrassed by the situation and I think I need for her not to snuggle too close to me any more, but I didn't know how to say it. So I figured the safest thing to do was to talk to my wife and have her straighten things out. I tried hinting around the problem, but somehow she wasn't getting it. I kept getting more and more direct until she got the point, but then her reaction surprised me. She suggested putting her daughter on birth control. What the hell am I supposed to make of that answer? Is this a trap? Is she waiting to see whether I will say okay? Or is she trying to say that she's really okay with the thought that I might do something with her daughter? I hope to God she doesn't sit daughter down and say, "You excite step daddy, so we need to get you on some birth control." That would be humiliating at best. If she told her friends and it got around the police, for example, it would be a serious problem.