They took her out for now and Aurtax posted on the forums a while ago (it was either him or waltzing, pretty sure it was Aurtax though) that they were waiting until they could bring her back without causing any problems, so i'd expect her to be back in the game next patch.
Yulia should be found in most major towns.
Also, from the bug report:
"The NPC 'Yulia' is missing from all major towns during the duration of the Marvel Machine promotion. (UPDATED: Yulia will be available after the 09/05 patch, and her quest will be available from 09/05 - 09/18)"