Mother needs help getting up but gets up by herself without calling, putting herself at increased risk for a fall.

I am feeling so frustrated. My 93 year old mother in-law has Parkinson’s and vertigo. The med she takes for vertigo makes her loopey and I know she needs extra assistance when getting up with her walker so I urge her to call me to help when she needs to get up. She nods and agrees that she will call, but often gets up by herself anyway. A few days ago I went to check on her and found her on the floor. She had gotten up by herself and fell. Thankfully unhurt, but someday may be different. This afternoon I found her up in the bathroom after she had agreed to call for help, but didn’t. She said, I just needed to see if I could do it myself. How should I handle this? It really aggravates me.