Sir I feel it would be very rude and it's just an opinion, since you are asking us and all sir.
XD
If you love her my friend, I wouldn't do that to her sir.
Treat her nice my friend, because none of us a perfect. But I am sure your girlfriend is a great person my friend, so show her love my friend.
XD
If you were thinking of doing this to motivate her, well I don't know my friend because you might hurt her feelings. So I feel you shouldn't cause it's rude but up to you sir.
XD
To each their own my friend.