I had a gf like this once, wanted to get married but she had other ideas, namely

1. Used me to pleasure her when she felt like it
2. Use me as a punch bag when she needed to lash out
3. Made me pay all the bills
4. Used me as support during her studies

Once she qualified she levelled up and no longer needed me.
She started looking around, playing the field, her loins got loose and I started noticing the GUY count increase in Facebook, then the messages "Did I do something wrong" from other guys.

She then got another job, levelling up looking for better prey.

Then found a new religion, joined a cult, experimented lesbian.

I then got the boot!

Tried to pull her out of that cult, it was the last decent thing I could do for her, but efforts got worse, started working against me.

Just backed out and moved on. She settled in with an odder more $$$$ model guy.

take it from me OP. You done your part and its time to enjoy life as difficult as it may seem. Its gonna be ok.