MIL KISSED MY BABY ON LIP

Help!! My MIL kissed my baby on the lip despite us telling her not to in the past. We told her that need to wash hands and cannot kiss baby. We visited her today and she remembered that she needed to wash hands (told me she washed hands before carrying my baby). Yet, when she played with my baby, I saw her purposely put her forehead close to baby's a few time then suddenly kissed my baby on his lip! I was so upset and angry. I quickly gave excuse to bring my baby away and wiped his mouth with wet wipe. Did not allow her to carry baby thereafter and quickly left the house. What makes her think that she has the right to kiss MY SON on the lips? We are worried about the hygiene issue! And now still covid period! Mummies pls tell me what you had done to stop this from happening again. This is a total nightmare and I am considering stopping any form of access with MIL to prevent this from happening. Totally disgusted!!