That sure is an awkward situation, which may be even more difficult depending on the nature of the "formal relationship". If that makes it truly impossible to even acknowledge your feelings, there really isn't much more you can do. Maybe it would help to bend someone's ear on the topic, and look for relationship-appropriate ways to support her. If that isn't a deal-breaker, and there's any way you can talk with her, you really should. She deserves to know for sure, and so do you.
Commiseration
*Hugs*