Pre-teen DDs in separated families

[NotaDisneyMum]

My DD has a 50:50 care arrangement with her Dad, both he and I have new partners.

DD is just starting to show signs of puberty; filling out, breast buds etc. She has had several education sessions at school, I have attended a couple with her, we've chatted about growing up and I found her a fabulous book recommended on MN that is well thumbed.
She is, understandably, reluctant to talk to her dad about these things, but I've explained that he knows all about it and it's been agreed that she will talk to stepM if there are things worrying her when she's at her Dads.

So I was a bit put out today when she shows me a book 'about growing up' that she says my exMIL gave her.

I feel that she has overstepped; it's not as if DD doesn't have a mother in her life, or that I've failed to support her in this, so why has exMIL got involved?
I'm not keen on the style of the book, either - it's rather 'old fashioned' IMO.

I know I can't do anything about it, exH and family are not receptive to discussion and will do their own thing - but will it confuse my DD if she is receiving two parallel educations about growing up that aren't coordinated? Would it be better if I left that side of her education to them?

[2blessed2bstressed]

You don't really want to leave it to them though, do you? I think in your shoes I'd look at the book and check that there's nothing in there that is incorrect or no longer relevant (not sure what you meant by "old-fashioned), and then just leave it to dd to look at if she wants. If your dd has already talked it all through with you, and has a good book at hand, then she'll probably not bother with the one from ex-mil anyway.