My wife an I recently hosted a woman becoming a baalas tshuva. she informed us that her Jewish mother had fertility issues, so her mother used eggs from an anonymous surrogate which were implanted inside her mother and from that pregnancy this baalas tshuva was born. I believe this is a machlokes if the baalas tshuva is Jewish. should the baalas tshuva be required to go to the mikva?
You are correct, there are different opinions about this, and this is something that the local rabbonim and bais din should deal with and should be brought to them. Additionally, you should also take guidance from them what should be said and when, because on one hand she should know this, but on the other hand you don’t want to discourage her from becoming a baalas teshuva.
H-shem should send you siyata dishmaya dealing with this delicate situation.