just go with it. Play with it. See where it takes you both.
Shag the arse off of her and make sure you fuck her, even if she whimpers. It sounds to me like she's gagging for a real man to fuck her.
Maybe she wants to be taken, like the first time. Or maybe you haven't sat and talked enough. Either way you need to find and trip the right switch in her.
Maybe, as it turned out for my wife, she is probably gay and doesn't know it. My wife does not want male affection, she can barely tolerate it. She has twin kids that came about the hard way, against her will. She has to be supported, she has two toddlers, but she is now aware that she has feelings for another woman, her crush is a nurse she met when she was being given lactating lessons at the hospital. I have this vision of this woman holding her breast and smiling at her. I have to get it out of my mind. It is not easy because they are now 'friends' and I have to pretend that nothing is going on.
try not referring to it as sex , try telling her that you want make love to her . there is a difference .