At a Loss with Stepdaughter

My stepdaughter is having some anxiety problems and according to the ex, showing some obsessive/compulsive behaviors.  She didn't give any examples though.  She also said that sd doesn't like her current therapist and wants a new one.  The ex also said she's really worried about her (but not worried enough to limit the number of honors courses she takes in high school, music lessons, etc.).  She is seriously panicked over school/grades. 

My husband mentioned today that my sd would tell me things before she'd tell her mother or him and that perhaps I could talk to her.  He is right...or was.  Five years ago, that would've been easier.  Now, I'm not sure how I'd do that if there is something sd wants to talk about from 200 miles away.  Texts, emails and letters aren't private over there so she's not going to open up under those conditions.  They learned at an early age that phone calls aren't welcome from our home.  That seems ingrained into them.  I know the ex wouldn't welcome my talking to my sd AT ALL by any means no matter what even though my sd did open up to me, did trust me, did love me, etc.  Sd showed a preference for me over her mother in a public setting, in an emotional way, several years ago.  The ex created that situation by making them feel like they had to choose between the two homes instead of just allowing them to thrive with both homes.  I doubt the ex would give that bond a chance to blossom again.  She seems to have things just the way she wants them right now...I feel bad for the kids.

My husband wants sd to come live here.  I doubt sd would leave her boyfriend at this point and the ex would never agree.  A change in environment might be exactly what she needs or it may make things worse.  Without any details, which the ex hasn't given, we don't know what behaviors she is exhibiting, what she worries about (other than her grades), etc. 

I don't know what to do to help sd.