Great grandma watching my 6 month old

I need some advise. My husbands grandma is in her early 80s. I’m not fully comfortable with her watching my daughter who’s only 6 months old but my husband seems to disagree and says she’s fine. She has fallen before since she has a bad knee and she raised kids 50 years ago, not in this world. I get nervous and my 6 month old is a lot to handle. Idk what to do about this situation. Am I over reacting?