Boyfriend flirting with bff?

So my best Friend tends to flirt a bit with my boyfriend and it always gets on my nerve. She likes to tag him in random things on Facebook and Instagram. She used to say 'we can't be talking like this' etc. I had a thought the other day that I could possible ask my boyfriend to flirt back a bit with her and see what she does to see if I could trust her. Is this a good idea? 

Vote below to see results!