But if Gillian « goes back to her old self » while filming s11 and then continues being with Peter what will you get out of it? I need your logic on this cause it’s very possible

It depends on what you mean by being her old self. If you’re talking about teasing and flirting on social media, it won’t mean anything as it never did before. It’s just fun and entertainment for the fans.
If you mean teasing and flirting in real life in front on cameras or not, well… I’m pretty sure that will happen because they just can’t be otherwise. I guess that’s how she’s always been with David while being single, in a relationship or married. I’m not going to analyze wether David did have or not something to do with her break-ups, but there’s one sure thing: all her partners/husband had to deal with him and their chemistry at some point. I don’t think PM had to deal with it for real yet, and he isn’t Mark, he isn’t Rodney, he isn’t Clyde, so God knows how he’ll handle it. Wait and see…