My mother allowed my sister to grab everything when my father died. Now they are turned against me. What should I do?

it all depends as to what happened or how they think things went down. try to talk things out with them and get a feel for their side of view, it could be a lot different. if they still won't talk to you, then i say forget them. a family member passing away is a time for remaining family members to become close and love each other more than before, to be there for one another. and if they don't want to fix that, then i say forget them. this is a time for you to grieve and take all the time in the world that you need in order to get through such a loss. either way, i hope things go good for you. that's always a really bad way for families to be separated in any way. i'm also very sorry to hear about your loss; it's never easy.

move on

Cut your losses. Get rid of them. Ignore them.
Either they will do anything to get you back or you find new family members.

For starters, ask your mom why she allowed it.

What did the will say? You can contest it. If the will didn't say anything, even better; you can sue her for taking everything.

Regardless, I'd talk to a lawyer to explore your legal options.

check the will