I don't think she's a goddess, else the more powerful Queen would easily be one. Eliette (who is a deity reincarnated as a mortal giantess) doesn't refer to herself as one, implying she lost at least some power, and Pyeka's feats are on par with Eliette's, if not lower than her (something something purification army).
Besides, Pyeka's evidence of being one is everyone worshipping her in her kingdom, which has happened IRL to many (not so divine) monarchs across the world. Trapping souls is something Nyxmay (and probably Makla) could do, and controlling stomach acidity isn't a huge deal either. Her feats are subpar for a goddess, and we only have her word which, given her recent updates of manipulating things from the shadows for her own ends, isn't really trustworthy either.
If anything she seems like a spoiled rich kid who created a cult of personality and believes in it herself.