Being stern with MIL?

So my mil has been stepping on me and pushing me around since I married her son. He is a total and complete mamas boy but my marriage was arranged and I didn't really notice it in the 6 months that we knew each other before we had to marry. One example is that her son is a smoker (my husbands brother) and i really dont like the idea of him holding my infant with smokey clothes. I tried to nicely ask him if he would change his shirt before holding my son and he refused saying that's crazy and my mother in law was like ignore her it's a phase. In the past I would have bit my tongue and just hated her inside but I busted!! and said no actually it's not a phase and it will never ever pass and if you can't respect my wishes don't hold my son with your smokey clothes at all thanks. That is one example here's another im breastfeeding my 5 month old and am newly pregnant again my milk supply has been fluctuating and so ive bought formula to give him after each feed incase he isn't full. didn't end up needing it but I was at her house one night and I had in mind to hide the bottle near the bed i was nursing him in Cuz i knew she'd overstep boundaries anyways she spots the bottle and starts giving it to him knowing full well that I was in the middle of nursing him and just got up to get something so I asked her nicely pleas dont give him the bottle i want to nurse him and she continues I said it again and she goes I just want to see if he'll take it mind you hes eating it of course hell take it cuz i wasnt finished nursing him! anyways again i just lost it maybe it's the preg hormones or maybe just enoughs enough it's been 3 years of this i said stop giving him the bottle now and gave her a stare of death she got up in a huff and left the room. I felt bad but like cmon I asked you nicely twice!! and she seriously has like no respect for me!! anyways what would you do? would you speak up? was it over reacting oh I forgot to add that when she wants to ridicule me she talks about me in another language thinking I won't catch on. I'm so sick of her! thanks for the comments!

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