How to cope when your mom lied about her cancer diagnosis?

Im going nuts. Im under so much pressure. My mom and I are not in a good place. I can hardly be around her or even talk to her.she kept her cancer in the dark. Lying about everything. We found out how bad it was at her surgery that failed because we had no clue. We could have prevented the unnecessary surgery If she would have let un in. She even lied about us not being allowed at chemo. I dont understand why. And I cant get past this. She doesn't have ling.