Sound advice needed

Its a long story to explain bear with me,
Plz help me to help my friend. My friend has his long time girlfriend of 3 olmst 4yrs nw, they are the most awsome couple you can ever think of, i envy them, but something strange happened, they met in college, they have leaved faithfully to each other, so this gal got a job were she works 5days a week o sometimes on a satday. So at her workplace another guy was stalking her, so on this particular saturday, this workmate deviced a plan, and offered this gal to go for refreshments, and she agreed on the basis that its a workmate, so they went out, to some public botanical garden. Then a relative to my friend saw her at this place with guy, then they kept quite, never spoke to her and she too didnt know them. After a while this workmate went on to propose to her, to which she told him i olredi have my boyfriend, had i known that thats wat u wr plannin i wouldn't have been here with you. So the day closz, on the morrow she gets confronted with the guyz relatives about yesterday then she tells here boyfriend the whole story, and even went to tell her dad about it. My friend forgives her and puts it in the past, then now its 3mnths past, the parents of my friend are told by those relatives this odeal, so they pressin my friend to rethink his decision of forgivin his sweetheart. He loves her stil, now this parents issue is now stressin these two. whats your advice to this? What action must my friend take?
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