Am I crazy?!

I don’t even know where to start with this, but since having my son I feel like my MIL has been placed on a different planet to me?! TODAYS ISSUE - I found out she has taken my two nieces to a soft play when they both have had noravirus in the last week and have just come out of hospital!! I am being crazy or is this completely selfish of her to expose other children like this? We are also planning to see them Sunday but now I just feel like I do not want to go anywhere near them as if my 5 month old ends up sick I will loose my mind How to do even approach this with my husband? He is currently in work and does not know. Do I bring up the fact I’m so angry about the soft play thing? Or do I just keep my mouth shut and mind my business?