ud--here's some advice you can take or leave. I spent almost 7 years doing pastoral ministry and bereavement care, so I am sadly familiar with the circumstances.
Calling and funeral are probably the biggest closure events; burial is probably less so, especially since we no longer watch the casket being lowered and covered. So if there's viewing and funeral but you can't attend the burial, you'll be part of the more significant rituals.
It would be fine for you to contact her family, unless you are on extrememly bad terms with them or they would have a tendency to blame you in some way. If it feels awkward to be at the funeral but you still need to be there, sit near the back. If you feel strongly about her having her ring, take the funeral director aside and explain the situation, and he/she will likely find a discreet way to make sure it is with her before the casket is closed. The alternative is to slip the ring into the casket yourself. I would imagine that unless the family has very bad feelings for you, it will be a comfort to them that you cared enough to come to the services. Even if the boyfriend is there also. Suicide is so very tragic and painful for all the survivors that at this point you have far more in common than you have differences. You'd be surprised how much reconciliation and forgiveness comes up during funerals.
I pray that you will be able to find some peace wtih this.
M60 H52 D20 M14 yrs OW-old gf from 1986 bomb-5/18/08 H filed for D-9/10/08 D final 4/24/09 xH remarried (not OW) 2012