that's a good question... i dunno if she would really be using a different name to attempt to hide from "us" though... us booting her shows is really the least of her worries (in my opinion). I think about it this way...
She has a guaranteed sale of her album with all of us, if not multiple copies.
She has a guaranteed promotion by word of mouth from all of us.
There is really no "harm" in us hearing the new material.. the audio recordings generally out there are not super great and multiple versions of the same song just interest us even more. Look at Kulp and his multiple versions of Nolita Fairytale fun
If i had to guess the reason she shys away from bootlegs is she seems to be a perfectionist and doesn't want audio recordings out there that are less than perfect for general consumption... I also think if she was going to perform under another name she would use one other than her sisters... clearly it didn't take long for us to be chattering about her potential performance
Maybe Gwen really is getting into something and/or perhaps Vanessa was just playing piano with Gwen?
Even on the other albums she always kept a few songs for the album and didn't perform them live. We also don't know if it was new material or just the same songs we've already heard... just lots of speculation.
-katia