So I heard a rumor, and I forgot where, that Leila has a pretty good function. She buys stuff for 1/20 of what Reese does, but there is a trick. Every item you sell to her consecutively that is the same daily, it gets a little bit more expensive. I've heard that the most she will sell for it will be about 50% more than what Reese will pay for it. However it can only be used for one type of item because if you break the streak of the single item, it will go back down to 1/20. Can anyone confirm this? I just thought that Leila was pointless and that kind of seemed odd. This seems kind of legit enough to be real. Don't think that I know if this is real or not, I have no idea. So obviously take it with a grain of salt. I'm sure that since the game has been out since November in Japan that people would know if this actually is real or not. I'm kind of thinking it's fake, but it's interesting either way. However, is it real?
I can't confirm the rumor you heard, but Leila is far from useless.
While I was diving, and trying to bring up one of every sea creature, I got a ton of repeat stuff that I didn't want. Since nothing sells for any worthwhile amount of bells, sans Lobsters and Giant Isopods, I found that selling them to Leila was a much faster alternative to releasing each one by hand.
Leila's main purpose, for me at least, is an easy inventory dump.