WIBU for cutting MIL out of our lives for comments she made about my 13 year old?

[DefinitelyNotAStepfordWife]

I'll start by stating that I can't stand the woman. I barely tolerated her for my partner and kid's sake before this and already wanted rid of her. There's no hiding that. Pretty sure she hates me too but I really don't care at this point.
On to my question: MIL came to stay over Christmas and asked lots of questions about 13 year old's bf. General stuff, what area does he live, does he treat her nicely, how old is he, stuff like that. Then started asking about if they've done anything yet, even so far as asking if she needs a pregnancy test. She's 13! I know kid's start earlier and earlier, I'm not ignorant, my sister got pregnant at 15 so I know this happens, but come on! She's 13! She blushes when talking about holding her bf's hand and he's only just turned 14 and is in a few of her lessons. It's innocent and cute.
A few comments were made by my partner and his brother about potentially scaring him off but this was said just to tease her a bit and my daughter just laughed and told them to shut up. My MIL then felt comfortable enough to tell my 13 year old that she needs to be careful how much of her new make up she puts on so she doesn't look like a prostitute or make her bf think she's "giving it away". I told MIL multiple times to stop sexualising my daughter but was repeatedly ignored.
Another time, Christmas day, me, my partner and MIL were talking about how the kids were getting tired and need a rest as they were all getting a bit worked up. This was after 13 year old and 10 year old got into an argument. I said how 13 year old shows her temper more when tired and how she was having a rough time at the moment, fall outs with friends, falling behind with homework, pressure of choosing her GCSEs ect, and MIL said "no, she's just a teenager, and all teenage girls are just b*tches". I couldn't believe it! Doesn't help that my partner won't say a word against her, even in defense of the kids.
This is after years of attention seeking from MIL and a lot of nasty comments towards me but this really is the last straw. So AIBU if I tell my partner I want her nowhere near our kids?

I was born in 68 and educated at a grammar school in a leafy affluent area. Thirteen and fourteen year old were certainly having sex. I don't know what makes you think they weren't?

She sounds horrific! Telling daughter she will look like a prostitute if she wears too much make-up and the b**tch comment .... pffft! Absolutely not. She's not a 'healthy' adult to have around your kids when she makes such comments and thinks it's acceptable. Let's face it, if you don't like her anyway, why keep contact and prolong your suffering? I would tell her she's no longer welcome to visit or stay in your home and that you and the kids will cease contact. If DH wants to stay in contact with her, that's on him but I would definitely cut her off and maintain your peace!

I was born in '60. Perhaps the kids at our working class comprehensive were that bit more naive.

I do recall that one girl became pregnant at 16 and was permanently excluded. Her boyfriend was allowed to stay on long enough to sit his "O" Grades (Scotland). I recall that the girls at the school were outraged at the unfairness of the girl being forced to leave. I assume that the school thought that she would set a bad example for the rest of us.

@Livelovebehappy

Surely you dont really think two thirteen year olds of the opposite sex can have a totally innocent long-term bf/gf relationship? It's not going to happen. Sex at some point will come into it.
Sure. AT SOME POINT if it lasts.

I remember boys and girls being bf/gf at 12/13. They didn't have sex. They hung out a bit. Called each other their bf/gf until someone got bored and they 'broke up'

You might have been all raging libido at 13 but I wasn't and neither were the people I was friends with. We were all really young and innocent and liked the idea of having a bf/gf more than anything else.

A lot, because I work with children from 4 to 16, mostly girls.

No, I went to all girls' schools aged 4 to 17, so Kindergarten to end of A levels.

Well I think that probably goes a long way towards explaining the relative lack of in-school couples.