was she ever this sexually charged during the marriage before separation, OM and divorce talks entered the picture?
I would say that she's having a ton of sex with you and possibly someone else and she's enjoying the attention.
She's having sex with you so that you don't start pursuing sex with another woman, it's very common and the technique is called "tagging" or marking her territory so that you don't have sex with anyone, she wants you to believe she wants to have a relationship with you, she knows you get emotionally invested and think that things will turn around and improve but this is her ego calling the shots and she doesn't have that intention, she's controlling this right now, you have to see that. Do you think if the shoe was on the other foot and you were the one pursuing her, sending her all these sexual texts that you would convince her to have all this sex with you? Not bloodly likely, she would shut you out, it would be a long cold winter for you. She knows she can get away with it because she knows you're still invested in her emotionally, you want her, you love her and she knows you want to have sex with her. She knows all of this and uses it to her advantage.
Prove my point, the next time she comes over to have sex with you, tell her you can't tonight, you're going out with a "friend", get all dolled up as if you're going out on a date, watch her reaction, she will be pissed at you, really angry, you'll be deviating from the course she has planned for you.