You need to switch gears, I'm not a huge fan of pushing her further away here, because that's going to help confirm her belief that you're not relationship material.
If it were me I'd take advantage of her being more vulnerable around the holidays and hang out more. Fuck, I'd get her to blow me every night! Be a pseudo-couple, just don't act too beta here (I know you won't) and definitely don't go doing anything stupid like buying her a bunch of shit for Christmas. Also, make sure to respond to her asking if you're boyfriend and girlfriend with either a joking, "We're whatever you want us to be." or "Let's not ruin this with silly labels." You could even add, a "We're not getting married tomorrow or anything, right?" Keep pushing that convo off and lie like crazy when you have to, as ElJefe suggested.
Meanwhile, the key is to keep
creeping on the side, so you're continually building and fucking other prospects. Then obviously get more and more distant again after the holidays, when her innate emotional need to be with someone starts to subside.
I think if you do this, you'll display your 'good side' long enough to her that she'll always firmly believe that a relationship with you is possible (even though it isn't), and you'll always be able to get her to come back.