I know how it feels to be "hidden" away from your significant other's friends and family. Even after 18 months, my now ex-SO kept me a secret (they were a bi asexual woman, I'm a straight, asexual guy).
The important thing is to remain respectful and to not pressure the other person. Make sure they are always comfortable. But, tell them how it makes you feel, its important for a healthy relationship to communicate. Talk about how it makes you feel, and importantly why you feel that way. Communicate how you would like to see things change and offer to help your partner. Clearly, they are struggling with coming out, and that is okay. Its important to be there for them too.