Honestly, I don't blame Fateh for acting as if everything's fine. That's how most people try to cope up with bad incidents. Add on to his realization that although Tejo supports his "getting over jasmine" mission, Jasmine's still going to be a priority for Tejo exactly like before which would be difficult to digest as it is. Although he somewhere expected that Tejo would forgive Jasmine the forgiveness came too fast and unexpectedly (since he doesn't know the drunk drama of Jasmine). In addition, the forgiveness didn't stop there, she literally openly declared that Fateh should forgive Jasmine as well in order to get over her. Well her order is completely reverse to what actually happens. When he finds out that his present life is giving him a sense of satisfaction that moment he would have found that Jasmine's presence or absence doesn't impact his life nor his happiness and in that flow would have forgiven Jasmine.
Now to the reason why he said he would forgive Jasmine, one possibility is that Tejo is his anchor and he respects her too much to not consider her opinions. The second reason would be that he doesn't want to lose Tejo, currently the only one who understands him completely just because he couldn't forgive Jasmine as Tejo wanted. So, in my opinion, Tejo's inconsideration is actually doing bad more than good although her intentions are pure.