Sorry I'm confused (NTA in any way btw!). She currently has control of the funds? Were they not transferred from the estate directly to you or is that what you mean, they were, but into an account which your Mother has access to and has taken control of now?

Are your parents no longer together and is your Father aware that the inheritance his Dad left you is being taken by her? If not together, I would strongly suggest going to your Dad, he could help you sort out a new account as well as a lawyer asap. If not, you need a lawyer like now before she squanders it away.

This is your money, no questions, and no judge (in their right mind) would rule in her favour. I don't see you losing as being a risk, I see it being spent as the risk here, you will win but if nothing's left it won't much matter. With a lawyer, your Mother may back off, if she doesn't they could absolutely submit an immediate temporary injunction where the funds are frozen until a ruling is made to protect the money.

If you do still have access but it's a shared account or she co-signed on it, you need to open one today and transfer the money...today!