When you can't keep your word...

My friend called me yesterday and wanted advice (I write a blog so I am automatically dear abby ) she said she had known this guy for a long time and had always liked him,that there had always been a chemistry between them but for years they always were friends until recently she is going through a divorce and didn't feel loved or sexy or even thought she still had it , so one night as she was taking to him she took him up on his offer. After a wonderful night she asked why he was always so hot then cold with her for so many years,he said he didn't want to mess up their friendship,she assured him that she was cool and that they would still be friends. He contuined to be hot and cold with her ,calling every day to disapearing for a week with no word.every time he would pop back up it would give her hope that something was there between them. When they did see each other she said there were always sparks and the way he sometimes looked at her would lead her to believe that there was more there. But recently he told her he was working on himself and was trying to change because he didn't want to end up alone , she was happy for him,change is always good.then he disapeared again for a week (during this week my friend realized that she really had feelings for him and realized it was better that he didn't talk to him ) things were fine and then he called out of the blue not once (she didn't answer) not twice but a bunch of times she told me "why is he calling I was just getting use to moving on " so she returned his call and what did he tell her that he went back to his ex! And proceeded to tell her that he was crazy he changed the ex didn't yada yada yada! My friend told me she was close to tears told him she wished him well hung up and decided that even though she said she was ok with friends with benefits she wasn't that she had real feelings for him and this was killing her so her question to me and my question to you is should she tell him or not she set it up the way it is but now can't keep her word. I didn't have a answer so I figured id write it down put it out there and see what comes back.