The statute for limitations applies for the time after the crime is committed until the time one is charged.
A prison sentence is not completed until...you do the time.
Yes, absolutely.
However, escaping from prison is also a crime, with attendant prison time typically added to the existing sentence.
While the law requires that the convict return to prison to serve out her sentence, it may be the case that the statute of limitations has run out on her later offense of prison-breaking. I am uncertain on this point.