My son's friend's father died several years ago. My son was a teen at the time and he just felt so weird about the whole thing (the wake, the funeral, sending a condolence card, etc). He had only attended a couple of funerals, for elderly family members.
I helped my son pick out a blank card, and in it he simply wrote "sorry about your dad" and signed his name. My son kept telling me that "kids don't do this" and that it was a really stupid idea, but I encouraged him to do it anyway.
The wake and the funeral were sad and joyful, as many such events are - laughter and tears and memories - and I went with my son to both. Of course, there was lots of family, and we only briefly hugged my son's friend, and met his mom and sister (just in a receiving line, I'm sure we were just a blur in a sea of faces). We didn't stay too long, as we didn't know anybody other than my son's friend. But we signed the guest book, chatted with a couple of people, expressed our sympathies to the family, and then quietly left.
However, about a week later, the friend ran into my son. When my son got home, he said "mom, guess that wasn't such a stupid idea after all. [His friend] said that he really liked the card and he was glad we were there. He said some kids didn't come, and now they don't know what to say and it's all weird".
So I guess that sending the card broke the ice, and when this boy saw my son, instead of wondering what to say or how to act, he could say thanks, which then allowed my son to ask how he was doing, etc. and they could talk, whether it was about baseball or how the family was doing.
I think the lesson is that if invited, it's good to attend a wake and funeral, even if it's awkward, or uncomfortable. My son's card was certainly not poetic or beautifully expressed, but it made the boy know that friends were thinking of him. And it made encounters after the funeral, such as at school or the mall, a little less uncomfortable.
Of course, no one WANTS to go to a funeral or wake, or to a hospital or hospice room, but to think of it from the point of view of the family, to think "my friend came" can be encouraging. And you might point out to your daughter that her friend will be pretty overwhelmed with emotions, with hugs from every aunt and cousin and friend of her mom's, and it might even seem like the girl barely notices your daughter, but she'll know. It's important. I would also help your daughter send a card, even as simply worded as the card my son wrote, to the family. When choosing a card, my son completely hated all the sympathy cards available (too "sappy", too "girly", too "stupid", I believe were the words he used), so that's why we chose a blank card with a simple photo on the front.
I hope both you and your daughter go, and send a card as well.