she should be around the same age as edith at 19-21.
preferably she should have a power but what kind is up to you.
it'd also be cool if she was a student of some kind.
pictured is sahara ray cause i rarely get to pic ship and they're adorable, but i'll accept most adorable ladies.
so basically ethel and edith met at a party. edith noticed ethel visibly uncomfortable by some guy trying to chat her up and swooped in pretending to be ethel's girlfriend. the pretending continued all night whenever one of them was clearly not interested in someone making a move on them. they swapped numbers at the end of the night and became instant friends.
their friendship consists of late night dance parties, going on adventures to find the perfect crop tops, helping edith make her soaps, and hijinks relating to edith being young and dumb and reckless and a party animal.
they start to fool around and hook up and develop feelings. they end up being that couple who's dating before they even realize they're dating. it works for them. even after they put a label on to it they probably still keep a semi-open relationship cause edith really like fooling around with her roommates, but we can talk about that together.
i kinda see their relationship being like this video where they buy a $100 van on a whim and go for a road trip, sleeping in the van. having camp fires and snuggling on the beach. sharing a bath together. more dance parties. re-setting edith's broken bones when she gets too reckless.
it'd be cool if she moved into the trash house at some point but again we can talk about that. nevermind all the rooms are full
most importantly though ethel should get along with most of edith's friends. this would mean she has to be outgoing and friendly and have a strong sense of adventure.