The constellation art depicts her with a Bident, but she isn’t carrying a new one in her main art? Do we have lore on her at all?
Called it on her name
The showcase art is depicting the gods' constellations which were presumably set in the sky long ago. Kind of a snapshot of the gods at their best, so that's why Thassa would still have her bident in her constellation. They won't change like the actual gods can when devotion changes them or they lose items. Hopefully we get more info on her new spearlike weapon.
I did consider that possibility as well, good point. I like how you explained it. I would like more information on her new spear and on her overall as well. I wonder if she has a blurb like Erebos and Heliod? I know Nylea and Purphoros didn’t sadly
The only real information we seem to have so far comes directly from the artist.
https://twitter.com/zack_stella/status/1213136494203793408
"I knew I wanted Thassa classically posed, and was tasked with creating her bident weapon replacement (it's now a Grecian-styled fishing spear)."
Thanks to DarkNightCavalier from Heroes of the Plane Studios for this sick Signature.