I'm a mother to a married son and a MiL to a darling DiL. I try to model my behaviour on that of my own late beloved MiL. What a gem!
I don't think there's a thing wrong with a mother making an adult son lunch or even 'mothering' him a bit here and there. It's no different than our mums mothering us when we need it. We all need mothering sometimes.
BUT she needs to be careful not to tread on her DiL's toes. And the DiL needs to be sure she understands where her MiL's behaviour is coming from. My MiL did things for DH, and I might do things for DS1, but NEVER would either of us imply that that means we love our sons more than their wives do or that their wives are somehow 'inadequate'. And neither of us feel 'threatened' by that mothering. Maternal love is different than spousal love. Both are deep and abiding, neither IMO is 'more' than the other, they're just different loves. And there is always room in a heart for two loves. My DH didn't lose one iota of the love he had for his mum and DS1 didn't lose one iota of the love he has for me when they married. Their hearts just grew large enough for both of us, wife and mum.
We stand equal in their hearts, each in our own place. But wives must and should stand 'just a little' in front of mums. And that's the way it should be! DH's and DS1's first loyalty is to their wives. When I silently 'gave' DS1 into my DiL's 'keeping' on their wedding day, I also took a small step backwards. I look to her, first and foremost, to be his joy and companion in happy times and his comfort and his 'light' during dark times.
Do I ever 'overstep' at times? Sure, but DiL has a way of letting me know, with love, that she's got things handled. And I take my step backwards and resume my place.
@Didntmeanto6 If you truly feel that your MiL isn't coming simply from a place of love for your DH, if you feel that she's trying to 'put you in your place' then you fell right into her trap. But you need to consider whether or not you've chosen to put yourself into competition with her and are thus hypersensitive to anything she does for your DH. It's not a competition. There is room for both of you. And if she does little things for your DH, that's not a 'slam' on you.