I love the idea that a former villain could just 'get over it' and get on with her life. Sure, she was created by Sinister for whatever reason, but that's all in the past. She's here NOW, and going all grr-vengeance-y on the X-Men is just playing Sinister's game and giving him even more power over her life than he already had. So to heck with it. Off to live a good life!
The best revenge is living well, they say.