Hi M.,
I'm sorry you are in this uncomfortable situation. Often when you choose something different than the parents or inlaws, they take it as a criticism, that their way isn't good enough for you. And it's not good enough, or at least what you want for your child, and they need to be able to accept that you aren't trying to say "You are/were bad parents" but that you aren't required to do what they did. Your husband really needs to assert that these are his wishes as well, because if you do something different than how your inlaws did/do it, they'll assume it's what you want, not your husband. Is your family supportive? If so, I'd use competition, let the inlaws know what while you are raising your child differently than how your parents raised their family, that your family is supportive, encouraging and cooperative.
There are some thing that are just different choices, such as not allowing ice cream cake and chips, but then there's just bad judgement, like giving alcohol to a baby. That's someone who you just can't leave your child with. And if your inlaws are "sneaking" your baby foods that you don't want her to have, I would not have them watch her either.You can let them know that it is fine for them to disagree with your childrearing, but that it is not their right to over ride your parenting choices. What benefit would a baby get from soda or cake? It's for the adults to enjoy watching the baby have them. It's not even like a 4 year old watching all the other kids having soda and cake, your baby does not know that she's missing these things (even so, it would be wrong of them to sneak your child foods that you don't allow)
While I wasn't that strict about foods, I did have to limit the time my kids could spend with the inlaws, because MIL just had such bad judgement. She didn't know when to set limits. She would take my daughter for the weekend when she was 3 or 4 years old, and take her to McDonalds both days for lunch and dinner. I didn't mind if she took her there once, but 4 meals? Her reasoning "But she likes it." When my daughter was 6 and went to visit them for a week, apparently she was drinking two 12-ounce cans of soda a day. My MIL had a cooler of them for Kayleigh in the car because "She gets thirsty when we're driving." Ummm, have you ever heard of a water bottle or a juice box? It's not like she didnt' know that we only allowed soda if we went out to a restaurant or to a party.
Have you actually spoken to them at a time when it's not confrontational? Not when it's a holiday or party and everyone is having ice cream and chips, but a sit down chat at another time when none of this is going on so that you can tell them what your dietary rules are?
good luck!
PS Debbie, I don't think that M. is saying that milk is bad, but at under a year, it's normal that her daughter hasn't had milk, as it isn't recommended for babies until they are a year. And if you're still breastfeeding, many women don't introduce milk at a year if they continue.