It's possible that some ovarian tissue was left, but it's more likely that she's just trying to play.
Mine do that sometimes, too...usually they have found one of their favorite toys and want me to get up out of bed and play. Miss Kitty is especially bad about it...she'll get one of her mice and walk around with it in her mouth, spewing those big, gutteral meows the whole time.
They also run round the apartment at all hours on a regular basis...it's just play and fun for them.
Miss Kitty did those things before Zoe was around, and taught Zoe to do them...so I have two little monsters to contend with.
Does she show any other signs of heat than the meowing and running around?