I don't really buy Remilia loving Angel, I think it's just a weird rationalization/mental gymnastics because author wasn't ballsy enough to have a solitary lesbo ending, 7/10.
While I would welcome a Yuri ending, the way Remilia loves Emi is beyond mere romantic love between one person of another, it's a mix of romantic love, friendship love, familial love, and a selfless and unconditional love.
Remilia doesn't just adore Emi, she
worships her. She views her as the paragon of kindness, the person who saved her from absolute darkness and the would-be savior for everyone else as well if not for Pina's interference.
You can see on the very first chapter that Remilia doesn't really have any sort of desire to keep Emi to herself romantically. Emi was wondering if getting betrothed to Willard was fine or not since he's supposed to be Remilia's love interest, but Remi says that she doesn't mind at all as long as she can achieve happiness.
If Emi could speak and wishes to stay with Remilia forever as her lover, Remilia would happily oblige. But Emi can't speak, nor did she showed any sort of desire for Remilia romantically either before she fell asleep. So Remilia prioritized Angel, as she thinks that he's the one person who can truly love Emi's Remilia and make her happy.
And Angel's love for Remilia isn't
really one-sided. As she had said in this chapter herself, if Angel can love this side of Emi's Remilia, then she can learn to love him as well, just that he'd probably never be her number one.
FYI this isn't really some sort of foreign thing, I don't think it's really any different as to how a mother would love her children more than her husband. Does she place her children as her number one love? Yes. Does that mean she hates her husband? Of course not, she still loves him very much.