Ok.. I have the ex dp staying with me for a while due to him leaving his gf and he had no where else to stay for a while till he sorts things out (we've split up for years but he is my dc dad and we still are civil to each other.. Odd situation I know)
Anyway, after splitting with gf he joined a dating site whereupon he had been chatting / what's apping a lady he met on there. Before they went on a date he has decided to get back with his ex gf. He says he has told this lady from dating site that he no longer looking for anything. Thy still met up for a drink and a chat. They are still chatting on what's app. He has not told his gf about this lady and won't be either as he says she wouldn't like it. (Wonder why!! 
Now.. I have said he needs to stop any contact with this lady. He says theres nothing in it just friendly chat and she knows he's not looking for a relationship.
I've told him he is encouraging her by replying to her messages and it needs to stop. He thinks it's fine..
If i was his gf I would be fuming he was doing this. Is it just me or would you not be happy with this either ? I've told him it's cheating but as he's told her there's nothing in it he considers it to be a like a colleague texting and chatting..
However.. He met her on a dating site. I think she thinks there may be something in it he's replying to her messages. She may not.. But would you repeatedly keep up contact with a man you met on a dating site and then told you he's getting back with his gf?
I wouldn't..
But I'm mn trained now :)
This is long sorry, just wondering who's right?
I think me but I've been known to be wrong!