I am sure you have the proverbial wicked step mother who is a piece of work and wants everything your father had any control over. She'd probably want back from you the money he spent on you growing up. That doesn't mean she's entitled to it or anything else. And don't give it to her just because she wants it or threatenned you.
If she has no grounds and takes you to court, that's actionable -- you could sue her back. And if she had some possible grounds, sure she can take you to court, and make things miserable for you, and expensive, but that does not mean she'd win. ANd you might be able to argue that YOU and not HER should get part of the other assets he had in a Will contest, etc.
It all depends on the facts. She'd have a very tough time claiming that if you are the beneficiaries of the life insurance she should get any of it. Typically states split up the assets of people who die without a Will 1/3rd to spouse and 2/3rds to all the children together (if there are 2 or more kids) so long as the spouse gets some reasonable amount. If she got more than a pittance, there better be good grounds. Get a lawyer and have you lawyer think about the choices. (It's a lot cheaper than giving her the insurance.) Your lawyer may be able to talk to her lawyer and end the matter quickly too. Otherwise she may have her lawyer write a letter to tell the insurance company not to pay the money as she has a claim. As insurance companies don't like to get involved in the middle of an inter-family dispute, they'd probably put the money on deposit in court and say let the court decide who gets it. You'd be best off avoiding that. Good luck, you should win 100%.
But don't be so and you can also take her to court to get the stuff she got and you didn't. have