@Mike E yeah she's trolling on my post and called me ugly names when i gave suggestion to a US citizen who got cheated by the ex wife who already got GC, to just move on with his life. she said that US citizen have to report to cops, ICE, USCIS, perhaps also to the president of USA if its possible. geez.
but to OP, that ex gf can report whatever she want, but if the relationship is real, i dont think ur friend gonna have problem. obviously do couple of meet up to strengthen their K1 case. the more the better