I think the sharing part will most likely be optional, but she still said it's something she wants to try, so it's not an ideal situation for me. It's like, you won't have to share her with another woman if you don't want to, but if you leave it up to her, she'll do it in a heartbeat... She's not just curious about it, she got horny because Milly touched her thigh, so one more love interest who doesn't think the MC is enough for her.
I completely agree about that scene with Julia and Deb. Not so much about an option to join and go for a threesome, but I think that even without and actual option there, if you were flirting with Jules from the start, she should have rejected Deb after she realised the MC wouldn't be involved. The whole "I hoped we would entice you to join us, but then I let her fuck me anyway" just made her feel cheap. Anyway, like I said what's done is done. Hey, at least Bart is still available...