Maybe I'm strange but... my female friends were always this way with me... they would talk to me about their periods, about bras and panties, things they found sexy, whenever they got UTI's lol.. and honestly... I've always loved it.. it made me feel like I belonged.. even before transition, before i even knew i was trans... I LOVED being included by my girl friends.. they would change outfits in front of me and they would show me intimate tattoos and talk to me about their sexcapades because they KNEW that i wouldn't respond like a pervy guy.. .they knew that i would show genuine interest and would actually give them constructive feedback if I felt it necessary... I loved it because I felt a sense of trust... something I never felt with my guy friends (or at least no more than ONE guy friend).
These days it's only become EASIER with my remaining girl friends as well as my young female cousins, they include me in their "feminine" privacy issues as if I was another girl and i honestly can't say that it doesn't feel great. Even way back then when I was as "male" as it got, my best friend Cindy would change in front of me, we would literally change in the same room if our conversation proved to be engaging enough, she would talk to me about EVERYTHING, she treated me like another girl despite me not even having a CLUE about my trans status...
In another instance, I went out to a restaurant and met one of my best friend's long time friend, and afterwards my best friend told me "she told me the funniest thing after we left" and i was like "what did she say?" and she says to me "she said that hanging out with you was weird because she felt like you were just another girl.. she felt like we were having a girls night out with us"... and this was also before even realizing I was trans (this was when I thought I was gender fluid)...
Perhaps you're on the other side of the fence when it comes to inclusion, but for me it was always comforting... even after discovering my trans status, it didn't really bring up any dysphoria with me, instead it allowed me to feel as though I was already a girl, and that I could have more patience for the transition itself. Probably a contributing factor to why I went Full time off the bat, I felt so much like a girl already that i felt weird wearing boy clothes

I would say try to enjoy it and try to consider it a sixth sense that they have, for all you know it might make it easier if you ever come out to them or if you are ever "discovered" because that way, they wont be surprised lol. But take that with a grain of salt