I'm going to tell my fathers ex-girlfriend to not submit a claim through his estate for money she said he owed her after he died
Will that work since she was only his girlfriend?
I tell you one thing she has always been ungrateful to my father. She piss him off like nothing else. He spent money on her career for years and what does she need more?
A girlfriend can try to inherit from the estate by claiming she was his common-law wife. She also may have rights to certain non-probate assets, such as jointly-owned property and money.
One way or another, she'll try to get something out of it.
If your father didn't want his ex to inherit any money, then that is his choice and you are right to respect his plans. His ex has no right to take what is his and it should fall to you and your family only.