Respect their relationship.
Don’t go around flirting with someone who’s taken or even try to homewreck. It’s shallow and disrespectful. They’ve gotten to where they are in the relationship from a long way and have been through so much, so they don’t deserve the extra bullshit coming from you trying to ruin their relationship. Flirt all you want, but with someone who is actually single.
One of my best friends was in the hospital last...