in my mind, aemond would not be above killing alyse's lover. so in that case, how would she react? since she is bound to aemond by marriage yk
He certainly wouldn't be above it. Alas, a lot of shit is going on all at once, he's barely in KL at all and when he is, Alyse plays her part (plus, he has his very own sideshow going down in Harrenhal), so he doesn't really care enough to do sth about it.
(Plus+, it's not like they're married for that long to begin with)
HOWEVER, if he did end up killing Gareth, Alyse would kill him. Plain and simple. She never wanted to marry him, she doesn’t love him, he killed the man she loves... She'll kill him 🤷🏻♀️