Deed has 3 names on it. Sister is half owner, parents are other half owners. My father recently died and my mother is very ill. When she dies, will my sister be the sole owner of the house or will I as half beneficiary in the will (my sister is the other half) get partial ownership of the house?

I'm sorry for your loss.

The eventual ownership depends on how the names are listed on the deed. If they are joint tenants with right of survivorship (JTWROS) then when one owner dies their share goes to the other owners and doesn't become part of the estate.

If they are tenants in common then when one owner dies their share becomes part of their estate and goes to the heirs.

You have to look at the deed in the spot right after where their names appear to see if they are joint tenants or tenants in common.