I don't want my mom kissing my baby on the mouth

I know, I know, there's nothing wrong with mouth kisses for babies, blah blah blah, don't judge people for that, it's not weird, it's not sexual.

My husband and I don't like kissing our baby on the mouth, personally. Just preference. So we don't. But I have nothing against people who kiss their OWN kids on the mouth.

But recently my mom has started babysitting my daughter sometimes and she's very, very touchyfeely and kissy, and I saw her kissing my baby on the mouth and it bothered me. Not only because I'm her mom and I don't do that, but because I know my mom has oral herpes. It's not like she was kissing her with an active cold sore, but I know that you can still shed the virus even without one.

I just don't know how to explain all that to my mom because she thinks nothing of it, really, and is GOING to take it personally somehow now matter what. I already have serious issues with my mom, but I have been trying to be on good terms with her for my daughter's sake and my dad's sake.

How can I tell her not to do that without making her feel victimized? Should I make up some other reason? Should I just be honest tell her it's because I don't want to risk my baby getting an incurable disease, even if it's not deadly or really harmful?