hello and good morning
my suggestion would be this
if you love him, really love him, then you would want him to be happy...and would do nothing to interfer with that happiness or that relationship now existing...
and whose to say, he would be happy with you in a romantic relationship?...remember for his sake, to ask yourself that question. If you interfer, in the present time, you might not only loose him as a perspective boyfriend, but also as a very good and dear friend?
as far as the sincerity of "her" love for him, allow the both of them to work it out...or not...
sometimes, we mistake the a dear friendship with the opposite sex, as a romantic attraction...later we find out, although we were very close friends, and we loved each other dearly as friends, we had nothing in common with each other....compatibility is very essential in a relationship. If you don't think somewhat alike on the same issues, there may be friction down the road???? If you don't enjoy or have the same interests, hobbies, down the road, you may go off in seperate directions...
If you allow him now,
all will work out, one way or the other,
in the meantime,
enjoy life and consider what you are planning to do for your future...
energize in other areas and have fun with life...
whatever you do, I wish you the best...and hope all will work out in the end, probably will hun, it usually always does. Be patient and don't interfer with the lives of others to gain your desires...if you do, in the end, you might end up one very sad person for doing so...remember, these are only my thoughts, the way I would handle it, you have to do what you must do...and learn from every action and step you take along the way.