If there's a wake/calling, it would be perfectly acceptable to attend. Believe me, I know funerals. If there's no wake, it would be just fine to contact her parents if you're still on any kind of terms with them at all, and ask if you might be able to attend any of the services. It would be helpful for your closure--and that isn't selfish, it's taking care of a need that will affect how you cope with this long-term.
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