She's reincarnated sure
Her fiancé is into his mate, sure
She's into it and wants to support them, yeah nice ! A yaoi but with the helper's view, why not !
But why does he need to hit on her then ? Not my jam, I'm more into fidelity, loving one person only, that kinda s**t.
That's my preference however. I find the situation to be sort of embarrassing to reed.