I dont know if elsa would be willing to share or if Eve would be willing to be shared. The only feasible option without going too off their characterization is constantly build up Circe and Elsa's relationship to the point Elsa thinks it wouldnt be too bad to share with CIRCE specifically which would realistically take many many chapters for it to not feel too forced (still feeling forced but not so much) and then another many chapters of essentially tempting Eve to go for a threesome AND THAT IS TOO MANY CHAPTERS INVESTED INTO JUST THEM HAVING A THREESOME, ITS TOO EXPENSIVE CHAPTERWISE, ITS NOT WORTH.