So basically your friend is ok with sleeping around under the guise of ‘seeing if we’re compatible’.
One thing we see on Catholic answers is exactly that. Someone has been dating, having sex with them a while, and they come on with some story. He’s spent time in jail, he’s been married before, he spends a lot of time drinking, he gets really really angry at me, he promised that he’d quit porn but he sneaking it on me now.
God made sex to be the glue to help married couples through tough times. When applied too soon, as in dating, somehow it becomes very easy to overlook huge red flags in a relationship.
Dating should be a time of evaluation of a relationship. Is this person a good fit for me, a good parent one day, someone who knows how to pray, goes to the sacraments. It’s a time to be sober and thoughtful. Once you have sex, hormones make it very hard to think straight.
There’s no regrets doing it God’s way.