She may seem happy now, but it won't last. I am a little further out in terms of the cycle. My told me immediately after the BD that he felt giddy (although I was in utter despair at the time and he knew it). He kept posting stuff about how happy he was. Fast forward several months since I kicked him out and it is now over a year from BD. Now he posts stuff that shows how unhappy he is. He is sending my kids weepy texts asking them to contact him. Looks can be deceiving.
People are telling you to GAL because the only way to make the pain subside is to have other things to focus on. Truly work on being genuinely happy. GAL doesn't mean that you are giving up on her. Who knows, maybe you will be back with her someday. Maybe you won't. The next 6 months, year, whatever will go by no matter what you do. Six months from now do you still want to be stuck and mad at yourself for not moving forward or do you want to be living a happier life?
