I had forgotten how the chapter ended and I kept wondering why people talked about training lol
Anyway, this manga definitely has a habit of making a mess of how it handles things, but I'd say this was a pretty solid conclusion to the Sarah issue (even if the arc itself felt a bit rushed). I'm actually kind of relieved that the boyfriend was real and she didn't just dump him to get together with Wakana, it's not often you see people actually moving on in manga... Also, with how abruptly this issue was brought up, I think it would have seemed cheap if she just appeared and they became a couple out of nowhere.
I feel that even if the author has actually thought of all these events beforehand (which seems very likely, since we had Wakana mention regrets way back in chapter... 9, was it?), they have a hard time introducing them properly into the storyline. I got the same feeling with the Mum arc as well: the incompetent parents had been mentioned before, but the timing of her actual appearance was just too plot-convenient to feel natural.
This was far from bad though, and I'm definitely looking forward to the training (now that I remembered about it XD)