Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
I am sorry to know about this concerning and frustrating situation
This has been an exclusive relationship , right?
and both agreed that you were officially dating and would not be looking for dating other people, correct?
yes. that's correct.
Then I believe the only assertive approach here is to confront her behavior, since this is inconsistent with your relationship
Her actions are not matching her words and commitment, and to find out she has not been honest is shocking, and must be addressed, not denier or avoided, or you would self-sabotage and expose to further dysfucntion
I can see you truly feel and believe you have this connection and have been consistent with it all this long, but now the problem is not about you missing something, but about her not playing a healthy role in this relationship, since she has been dishonest.
You're very welcome
I suspected that you would advise to confront her. I fear the trust between us needs rebuilding.