What should one do if one is interested in working on a subfield not within her advisor's expertise during PhD? I'm still in 1st year but have been working with current advisor for 2 years before PhD. I just become really interested in this other topic. The final PhD advisor pick is not confirmed until 2nd year but I feel it's not right to "abandon ship" because the advisor was main reason I was here in the first place. Plus I have become "estranged" from my advisor. We met twice in the past year and is not working on anything together. Usually it was me who read and work on things and approach her for a discussion. But since I shifted my attention elsewhere, this link is broken. She was like a friend who would occasionally check in on what you are reading and are doing what, as opposed to someone who guides you on which research question is important in the field and which direction you should and should not go. I feel it is right to approach some other people because I can genuinely use some expert guidance and I'm sure she wouldn't mind it too much so long as I eventually kept her as co-advisor. After all, most her previous advisees did the same thing because of her hands-off style.
The main issue is when I approach professors in this other field, what should I say? Do I just ask if they want to advise me directly or do I beat around the bush by talking about a "potential research question" etc as an interested student as opposed to someone who is looking for an advisor. Also how should I address my relationship to the current advisor? In fact, I think whoever I approach now will become the primary advisor. Should I just present myself as a "vanilla" student who is looking for full, devoted advisory or someone who they will advise on a shared capacity?