I know how you feel - I have similar issues with my MIL. Your DH is right, that she does THINK she's doing the right thing, but that's not the point. It's fine for her to think you are doing the wrong thing - I think most MILS do think that about their DILs, and part of it comes from the difference in recommendations and medical advice from when they were mums. I understand that. But it's NOT ok to act on it and do things against your wishes. My MIL feeds my boys things I'd prefer she didn't, and mostly I let it go as it's minor (but I do pull her up for spoon feeding my 4yo who is quite capable of feeding himself but knows that nanny will cave, and then expect all of us to feed him at the next meal!!). But I would not have let it go if she was feeding a baby those things. I would be livid in fact.

I know how hard it is and your DH probably feels like he can't win. But you do need to make it clear to both of them that there are things that are acceptable (such as grandma giving a toddler or pre-school kid a chocolate or similar treat), and some that are not (introducing a new food to a baby without your permission). Grandparents will be grandparents, which is why I pick my battles and let some things slide. But with most things, every member of the family knows where the line is that they are not to cross. I hope that makes sense.

GL hun. It's not an easy one.