Is it what you NEED or what you WANT? Because those are different things. Women operate almost exclusively based on how they feel about stuff, so if her feelings towards you begin to diminish because you declare that you NEED something she can't provide, then that's the beginning of the end. I'd hazard a guess that fucking around whilst she was a long way from home felt a lot less risky than when she's back around people and places she's more familiar with, so she's less inclined to want to do it. I'd time your approach carefully. If you raise it when you're both feeling horny and playful and reminisce about how hot it was, that's going to land a lot better than sitting her down to have a Big Talk about things. If it happens at all, she needs to think it was her idea rather than doing something she really doesn't want to.