All day long, every single time ds picks something up or shows interest in a toy, dd snatches it away from him.
I explain to her that we don't snatch. I tell her that in this family we share. I don't let ds take things from her either. I talk about taking turns ("No dd, right now it is ds's turn with that piece of fluff from under the sofa. He found it first. In a minute it will be your turn.") I allow swapping if ds is happy to be fobbed off with whatever rubbish she has grabbed so she can take the thing he was playing with away from him.
It is not about her actually wanting whatever he has. She just cannot stand it if he has something she does not have. It makes me sad, because I think it means she is feeling very jealous of him. I don;t understand why. She gets individual attention and one-to-one time with both dh and I. We don't make more fuss of ds than her.
I know it sounds like a small thing, but I know my girl and it is not like her. This is a symptom of her feeling cross and jealous. She gets furious when she is thwarted in snatching from him, and that is not like her either. She has become very sneaky about it too. I think this absolutely frantic snatching of EVERYTHING he has the second he has it really needs to be sorted out, and what I am doing about it isn't working.
Could you increase the amount of attention you give her?
Could you involve her in a game/activity for 'big girls', ie making her feel a little superior being able to do x, when ds can't? Sounds horrible, but I hope you get what I mean.
Could you make ds wait a little bit before you go to him so that she sees her needs/wants come first occasionally? I'm thinking if ds wakes up from a nap and you're playing with dd, just to finish off what you're doing rather than instantly leaping up.
You sound like a very fair parent and loving parent.
if it was me i'd go one of two ways.. i'd either have a serious chat with her and make a plan together that if she doesnt snatch each time ds has something she can get a sticker.. then do lots of praise and after a certain amount of stickers get a prize?
or I'd reach the end of my tether and come down firm on her. naughty step every single time she did it or removed from the room, until she gave up.