My SIL is a teacher and has no DCs. When she comes to visit (only a few times a year thankfully) she drives me nuts because she speaks to my DCs like a teacher would in a big teacher voice and tells them off while I am there and in their own home! I dont let them them get away with much and i dont know why she feels the need to step in- she just goes into teacher mode and takes over before I even get a chance to speak! She prides herself on being a strict teacher.
My DH and MIL had words with her before about this but she just can't help herself. I've bit my tounge a few times on family occasions when she's being 'Miss' to my DCs. She has a strained relationship with DH anyhow and the slightest thing could set off an argument so I let it go. Now it's really getting to me because I can see it is affecting negativley how my DCs feel about her or maybe I should welcome her input as an experienced teacher and I'm just being too soft?