Should I tell him about his lying fiance?

Super condensed version of story:

-Girl is in a 3 year relationship with a guy.
-Girl meets guy J on holidays in another country.
-J and girl have a fling and decide for J to visit her after she breaks up with her boyfriend for him.
-Girl meets guy M on plane.
-Girl dates/sleeps with M until J comes for his visit (so about 2 weeks) all the while making M sound as if he was her soulmate and that she was/had falling in love with him.
-J comes for his visit and guessing they planned out their future and he returned back home until he could permanently move back for her.
-M and girl go on two dates (they didn't sleep with each other, but lost of kissing/touching).
-On the breakup date girl makes M sound as if they're soulmates again and says they should try again in the future and wouldn't let M leave, the date continued for 7 hours with lot's of kissing/touching and I emphasise how above and beyond she went to make M sound as if he was perfect for her.
-Girl and M stop talking/dating.
-Girl and J get engaged a few months later.
-Does J deserve to know about M?

For the full story:
Tell him
Vote A
Forget it and move on
Vote B
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Should I tell him about his lying fiance?
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