I don't think triplets should all have names beginning with the same letter. It just looks silly to me and as though the parents have deliberately chosen those names, not because they like them, but because they begin with the same letter. Although these names aren't my style, I think the E, F, G thing is ok (you know
Evangeline,
Francesca and
Gabriella. [I like
Evangeline but dislike the other two]) and I don't think it looks totally intentional. I think that your friend should just pick out names that she really likes.
My favourite sibset from the ones you've chosen are
Niamh,
Molly and
Joanna. I think its cute to have subtle themes in sibsets eg. giving twin girls flower-themed middle names eg.
Violet and
Heather,
Lily and
Rose or you could use colour-themed names instead eg.
Siena and
Xanthe or whatever. If I had to choose names for triplets right now it would be:
Zahra SoleilEve ZephyraNaomi Rain
I've chosen three names I love as first names and three middle names I also love (all weather-related in some way to show what I mean about cute themes).