Both where very happy for their sister! Both knows Emira has been pinning on Viney for a while but their first reaction would be so funny. Edric would be like YESSSS WE'VE BEEN WAITING A LONG TIME and Amity would be like "finally".
I also headcanon they put their bets on who would ask the other first. Amity bet on Emira and Edric on Viney. Edric won and Amity paid for their first date (which is actually pretty funny because they had already a gazillion dates but well, this is the first one as girlfriends).
They also bet on their marriage proposal and Amity won this time (she bet on Emira again because she trusts her sister). Once it was made public Edric was a ball of tears.