NOTHING you wrote is normal grandparent behavior. ALL OF IT is overstepping, boundary stomping behavior.

OP - I say this from a place of caring. Cancel this shit show event. Tell your husband MIL can not come over, can not use your baby as a prop for her Christmas card.

Stop letting this woman RUN YOUR damn life. You and your husband are allowing this bad behavior, please put a stop to this entitlement to YOUR CHILD.

So to recap. 1. Cancel the whole thing. Her purchasing a Santa suit is her stupid tax.

1. Tell her bluntly that she/they are not allowed to use any photo of your child for her family Christmas card.

You said " I want to pause here to say I understand that including grandchildren on Christmas cards is common. "

It's only common with BSC grandma's who lay ownership to their grandchildren and try to make them do over babies.

1. Throw away the outfit she bought.

2. Stop sending her any photos or videos of your child.

3. If and when you see her do not allow photos to be taken.

OP- You only get these moments with YOUR CHILD, do not allow anyone to steal them away from you. She is stealing a FIRST from you. Pictures with Santa is a parent first. Not a grandparent first. If you allow this shit show to continue this woman will continue to steamroll right over all your moments with your child and make it about her.