Reddit mentions of Masterminds and Wingmen: Helping Our Boys Cope with Schoolyard Power, Locker-Room Tests, Girlfriends, and the New Rules of Boy World

You sound like an amazing step dad! I think you should keep on keeping on.

Keep in mind that teenagerdom brings about interest in sex. So it is likely a weird thing for her to even consider loving you at this point. She's now trying to break away from her child self and grow into her adult self. Love and loving physical contact with parents starts to get weird, add in that you aren't her bio and... I'm sure you can imagine how mixed up that can make a person feel.

If you feel like you are both having a good time and she wants to hang out, keep doing it, having a bond with you will be good for her in the tumultuous teen years to come. If you feel like she maybe isn't as into it, keep offering with sincerity and don't let a no hurt your feelings. It has everything to do with being a teenager.

I would highly recommend reading Get Out of My Life, but First Could You Drive Me & Cheryl to the Mall: A Parent's Guide to the New Teenager, Revised and Updated, as well as Queen Bees and Wannabes, 3rd Edition: Helping Your Daughter Survive Cliques, Gossip, Boys, and the New Realities of Girl World, and for the boys Masterminds and Wingmen: Helping Our Boys Cope with Schoolyard Power, Locker-Room Tests, Girlfriends, and the New Rules of Boy World.

Not teaching specific, but I found Masterminds and Wingmen to be quite informative.

You might find the book Masterminds and Wingmen by Wiseman helpful, for explaining the behavior and giving ways to help him deal with it.

https://smile.amazon.com/Masterminds-Wingmen-Schoolyard-Locker-Room-Girlfriends/dp/0307986683/ref=tmm_pap_swatch_0?_encoding=UTF8&qid=1486150730&sr=8-1