Spoiler
Does sleeping with Minthara, then breaking her neck, lock you out of other romances?
Is it possible to break her neck, then trigger Astarion’s romance scene later in Act I?
Can you romance Astarion/Shadowheart/Lae’zel in Act II after sleeping with Minthara?
I know not killing but sleeping with Minthara still allows you to romance others.
So I imagine killing her would just be added security in that case.