I think part of the question is, how do you define sexual behavior? Usually, sexual behavior is defined by intent (until you get explicit). Tickling, for example, can be completely non-sexual as we all know, but if done with sexual intent, it can be a precursor or foreplay to sex.
The issue with Mary and Anna is, they do not have this sexual intent. I asked Mary point blank and she said neither of them have a desire to do anything that involves removing clothing. And, they still love each other in what could be described as a romantic way, desire to spend the rest of their lives together, and want to hug/cuddle/share touch primarily with each other.
I come back to: does the absence of sexual intention remove any moral issues with this situation? If not, what, in clear terms, are the moral issues?