My friend needs help please help me with what to tell her to do

one of my friends have made out with a guy and they've done other stuff too...well they guy asked her out but she didn;'t really say anything..and he knew she was with david but he thought they broke up..so he thinks that him and her are together now..and so she with both I guess..but she likes JOhn more and the bad thing is he is like into smoking and drinking and will be going back to florida in like 2 months and David is total opposite and would enver even dream of doing that sh*t and David will always be here unlike john who is going back ot Florida in 2 months,,and she knows its bad but I want john while he/s here but then she wants to have david when john leaves.......what can I tell her to do?

well I think she only wants david for the sexual tention.. and this john kid, she should talk to him about his smoking and drinking and tell him it bothers her.. it will do them both better.
\thanks/