I think she means that come November, it will be a full five years that she's been dealing with her MIL.
Here's my opinion - those are YOUR kids. NOT hers. It is not her place AT ALL to make comments or be judgmental of you in front of you. I can relate. My MIL clearly disagrees with some things that I do. It has made me feel on the spot at times, and it definitely gets irritating.
When my MIL makes comments, I comment back. For example, if she were to tell me that I"m starving my baby, I'd tell her exactly what you told us.
There's been times that my MIL is trying to hold one of my kids, and if my child is visibly upset, I"ll take my child back (usually this applies to my babies...and my MIL does NOTHING to try to calm my baby. She just sits there doing nothing with the child on her lap, letting him/her scream, so I'll smile and take baby back). Anyway, there's been times my MIL won't let go of my child, and I'll have to pull the baby out of her arms. Those times I haven't said anything, but in the future, I will.
But there have been times she'll make little comments like "Well, I wanted her to get used to me holding her." Letting me know she doesn't agree with me taking my baby back. I just say, "I understand, but if my baby is crying and not settling, I'm going to take him/her back."
I don't let her view of how I should parent disrupt how I parent. I have confronted my MIL about things. She's an avoider when it comes to working out problems (self-admittedly). She will cause huge problems, and then refuses to apologize or work on things. She will only play victim all the time. She drives me crazy. I know I"m probably sounding mean, but I have tried SO HARD with my MIL. She is very hard to get along with with several people.
You could also confront her straight on about it. If she says something again, bring it up to her and tell her how you feel. She might not realize she's doing it to you?