Falin is like 14 here and Marcille is like 40 so nice age gap but regardless In that panel its from a chapter about how Marcille wanted Falin to enjoy the same romance series as her (basically elf twilight) and she was kinda annoyed at the human rendition of it. In the end she was glad Falin her best friend enjoyed it. There was nothing at all to imply any attraction.
Not only is there MULTIPLE panels of relationship charts shown throughout the manga, Marcille has flatout shown the type of man she IS attracted to and Falin considered marrying a MAN.
Marcille is 50 years old and Falin is like 22, Marcille met Falin when she was like 40 and Falin was like 12 and was the first real friend Marcille had, Marcile sees her as a little sister and also due to her trauma she is very overly protective of her. there is absolutly no single indication of any form of attraction or wanting a relationship with either of them.
You will never be a woman