If Eidolon City is an illusion - does that mean my Aspect character isn't real?

Short answer: yes.
Aspects are very real within the confines of Eidolon City, in fact within Eidolon City there is no discernible difference between any of the citizens, whether they be Aspects, Dreamers or NPCs. The difference is that only Dreamers exist in the Real World. Aspects and NPCs have no lives outside of Eidolon City. If all the Dreamers were roused from their comas then Eidolon City and everything and everyone else in it would cease to exist.