Let me kill that hoe who most likely stole that letter to give to MC's friend!! (ಠ益ಠ)
I see this is the start of a whole big misunderstanding. MC probably thought it was the guy who gave the letter to her friend but ML probably doesn't know anything, will likely return from camp to find that MC is gone with no explanation.
The friend doesn't seem like she'll give MC the chance to explain herself and MC is going to do the same to ML.