1) So is this the first time your Mom disrespected you and overstepped you and gave something to your baby????
2) She did it intentionally. That would piss me off.
But I don't understand... was your Mom holding the baby or you? Or was baby in a high chair? The reason I ask is: if my Mom was about to do that... but I was holding my own baby... I simply would have stood up and carried my baby away. So Mom would NOT put that fork in my baby's mouth.
So I don't understand... "how" your Mom, actually go that fork of frosting, in your baby's mouth, after you EXPLAINED to her, about his allergies etc.
And instead of reiterating to your Mom and debating to her ,about your son's allergies... just say NO to her. Don't explain why. JUST as your Mom was putting that frosting fork toward your son, I would have said NO... NO frosting and I would have scooped my baby up and walked away before she got that frosting fork in his mouth.
3) Your Mom... seems to have done that... in order to IRK you. On purpose and to on purpose, annoy you and get you irritated and mad.
She didn't do it for baby. She did it to get you, mad. On purpose.
She did not seem, benevolent about it, at all. Nor respectful.
4) I do NOT believe in the notion that Grandparents are supposed to "spoil" their Grandchildren with sugar or treats. That is not their "job."
My kids' Grandma and their relatives, do not do this with my kids. They ask first, if they can give my kids something. There is Diabetes, in my family.
And they do not know, of whatever allergies my kids may have.
There are other ways to "spoil" Grandchildren.
My kids' Grandma/relatives, do not do it with sugar or sugary treats. They "spoil" my kids in other ways.
5) The issue here is: IF your Mom, routinely disregards you and disrespects you... about your baby, then SHE is having problems with you and her own personality issues, and is against you for whatever reason. AND... in turn, she is also... disrespecting your Husband... he is the baby's Dad.
Sure, pick your battles.
But to me.... your Mom was not being kind or funny or benevolent, when she did the fork in your baby's mouth with frosting, stunt. Even after you reiterated to her... about your baby's allergies.
I would not leave your baby alone with her.
There is no way to predict, what or how she will feed him.
She obviously ignores what you say. About his food intake.
Thinking forward:
What happened with the frosting in your son's mouth... is but one incident. So, you need to know... how to handle it and your Mom, from here on out and in the future. Your son will get older each month and year... and you need to get some boundaries out there, with your Mom. Sooner the better. You and Husband are the parents.
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**ADDING THIS: as my kids got older, from 2 years old... I TAUGHT my kids, that me and my Hubby are the parents. That we decide things for them. Not others. Not even Grandma. So basically, we taught them the "totem pole" of adults in their life. And so that... THEY did not get warped ideas about what they can/cannot do, or eat or get or buy or so forth. My kids, will actually TELL their relatives or friends "I have to ask Mommy/Daddy first..." and they will even tell Grandma "Can I use your cell phone to ask Mommy first?"
So, basically, I have taught my kids how to DISCERN offers, to them, by others. And how to say no. And how to speak up. And HOW to know... the "pecking order" of what is offered to them to eat or wear or buy etc.
My kids are 5 and 9 now... and they are good, at it. In a respectful way.
My kids have this one bossy Aunty though. And even if their Aunt could be offering them a HUMUNGOUS chocolate covered mountain of a dessert at a fancy restaurant (which Aunty did do this one time)... my kids WILL tell Aunty "I have to ask Mommy first..." and they will call me. Or they will say "I'm full... I'm not in the mood for that. Thanks anyway." They don't let Aunty boss them. They know my/my Husband's "rules." And they know... Aunty is bossy and will try to get them to eat things. Although Aunty loves them and they love her.
So because my kids, speak up.... bossy Aunty has "learned" that she can't push her weight around, nor by-pass, me.