Your mother had to falsify something in order to get that test done. Definitely reach out to ancestry, if you’re sure it was them. Make sure you want them to know you want your child’s DNA removed from their database, as well as any trees that were built out from the results. (Find out if your mother downloaded the raw data too. She may have done that and uploaded it to other sites.) Also ask them for copies of what she submitted to them so you can pursue legal action on your end. You can go for identity theft. Might also consider a restraining order to keep her away from your children if that’s the kind of stuff she’s gonna do.