"She kept working."
Translation:Ze bleef werken.
In the past tense you never (not any I can think of at the moment) would get a -t at the end of the conjugation. Have a look at the conjugation of blijven: http://www.verbix.com/webverbix/go.php?D1=24&T1=blijven
And have a look at this topic: https://www.duolingo.com/comment/3846350