" Flirting " is a worldly and man made adulterous tradition who shouldn't be part of a good christian behavior.
" Flirting " should never exist in the first place. " Flirting " means fornicating, and fornicating means committing adultery, and committing adultery means cheating on your future or present spouse.
" Flirting " is the devil's work and Jesus said He has nothing in the devil.
So there is no true love in " flirting ", there is only lust in love's clothing who comes only to steal, kill, and destroy !
If there's false prophets, there's also false lovers and false friends.
If the Lord told us to not believe every spirit and to test every spirit for there is many false prophets in this world,
the same is to be applied in the private life to identify false lovers and false friends, and to stay away from them.
So how do we recognize false lovers and false friends ? Just as the same as with the false prophets, false lovers and false friends will be recognized by their fruits, and their fruits are ephemeral and conditional false love, selfishness, self-pride, lies, deception, and so on.
Just because someone tells he/she loves you does not mean anything until that person shows what he/she really feels by their deeds.