After getting Serel's Boon the first time from visiting The Salty Mast, then losing it from resting later on, the option to pay Maea to get it again seems to be gone. Seeing as I haven't actually started Far From Home i'm assuming this isn't intentional and is a bug of some sort.
Serel can still be talked to, but she only has her dialogue for after you've gotten her rest bonus, with no option to get it again.