Same thing happened to my close friend...( wife's last name different from primary) ...
His wife's application got approved 2 weeks ago... She received approval notice and card with status showing derivative E27.. .his is still pending
He is calling TSC IO almost everyday... everybody is accepting that its a mistake but they can do nothing about it.. and that he has to wait and don't know till when..
He used EAD but his wife was on H1B, now she is forced to use GC. TCS IO also told him that if his case gets rejected for some reason, then they both will be out of status... they have no status to fall back to...
Take an infopass appointment and see if they can contact TSC IO. Other than that, there is nothing much you can do... just sit and wait...