"You are nice to me."
Translation:Jesteście dla mnie mili.
Jesteś refers to one person, so it can be followed by "miły/miła" (m/f) depending of the gender of the person you refer to. "miłe" (n) is possible, but referring to a person you are talking to with neuter form is rare
Jesteście refers to more than one person, it can be followed by "mili/miłe", depending on who is in the group. (if there is one man in the group - mili, all women miłe)
Well, that would need quite a specific context. I can imagine "- Nie jestem miłą osobą, ranię ludzi - Dla mnie jesteś miła..." ("- I'm not a nice person, I hurt people. - You are nice TO ME..."), but even that could be said with a normal word order, just more emphasis.
Also it could potentially mean "You are nice in my opinion".