You are the only person who can answer that question, as to how you would feel if you did or didn't go.
One thing I would say though, could you perhaps offer to help her dad, or her siblings? I've been to too many funerals now where the celebrant/vicar sits down with family, gets a few highlights of that person's life and creates a eulogy based on a person they know nothing about, it can be quite sad as someone who knows them well to listen to their life boiled down to a long monologue of where they went to school, what they did for work etc, most of which can be largely irrelevant to what made that person special (and sometimes incorrect), just for the sake of filling a 35 minute time slot.
The nicest ones I've been to, where they really capture the spirit of the person, are the ones where family and friends have all had some personal input into the order of service, by way of poems, readings, music and stories etc, also, nice pictures as a visual tribute, which her dad may not have access to.
He may need some help but not want to ask for it.