I think yes, yabu whenever it concerns MiL's cos it's always a post about a MiL wanting to be granny or something but only OP's mum is good enough for that.
Stop being so fecking precious, she's your dp/h's mum so she obviously did something right or you wouldnt be with him.
It's all about ego and wanting to be the most important woman in your dp/hs life.
Get over it.