Corporal Hart is Sergeant Cortez's sidekick in TimeSplitters 2, until she is killed by a Reaper Splitter. She speaks with a strong Brooklyn accent and has various robotic body parts. While Sergeant Cortez jumped through the Time Portal, Corporal Hart stayed at the controls at the Space Station. However Corporal Hart was killed by the lightning bolt of a Reaper Splitter near the end of TimeSplitters 2. Despite this, she is the secondary playable character in Space Station, which takes places just after she dies. In the description of this level she is said to be in a different dimension where she didn't die.
However, she makes a reappearance in TimeSplitters Future Perfect, supposedly because the destruction of both the TimeSplitters and the Time Crystals at the hands of Sergeant Cortez erased all of the former's activities in humanity's past; ergo, Hart was never killed on the Space Station and consequently lives on.
A major change Corporal Hart encounters between the two games is the staggering transfer of her servo-enhanced Tritium Exo-Arm, changing from her left arm in TimeSplitters 2, to her right arm in TimeSplitters Future Perfect. There is no in-game explanation for this. Explanations differ from a Free Radical Design instigated joke, to the events of the TimeSplitters eradication in TimeSplitters Future Perfect leading to a change earlier on in her life, losing her left arm rather than her right.
A time later after Cortez and some Splitters join the heroes, the heroes find a Parallel-Universe Corporal Hart. She gets happy to see that Cortez is there, and introduces herself and joins the heroes.