I agree, but if this couple believed that, they would not be in a situation that allowed her to search his bedside table and find the ring.
Under the “tradition” I was raised under,
the very act of having sex marries the couple,
the ritual and oaths are window dressing
Subsequently one is VERY careful who they have sex with,
for one is forever afterward “One Flesh”
Just the fact she was rummaging around in his stuff should be warning enough.