If Syla went to the same place MC went (deryl comments on it being shady af but fancy).....then I don't think they were curing monsterism......
Unless Ella knows MC at some other point in his missing history that's the place they first met, probably where she met tanos (guess based on her looking younger in that photo), and the place where "her plan" was hatched. It would be the biggest twist in the game if they were legit good (or even not bad) people
Logically that group would have to better "monster focused medical stuff" than xanthe since all he can do (with decades and all of heros resource) is prevent corruption if you wear a helmet (for at least 6-8 hours if mc sleeps normally). Curing corruption would have been "helpful" for hero as well considering Henri/Nyx.