when you try tricking someone into doing something like this, you are opening the door for her to hide things from you if she does do it. it can also make people feel guilty or resentment. this isn't about manipulation it is about you two exploring sex and your relationship together. if she isn't interested, she simply isn't. It doesn't mean ever, it just means right now. she needs to feel comfortable with the idea then she will be more likely to do things. just keep in mind, once it happens there is no going back. you can be opening a can of worms you couldn't have predicted. focus more on her wants and concerns more than your fantasy. not doing so will more than likely having this backfire on you.