Carol Preston

Carol Preston is one of the secondary antagonists of the television series Timeless. In the original timeline, Carol had two daughters, Amy and Lucy and diagnosed with lung cancer. However, after a trip to the day off the Hindenburg disaster, Carol wasn't sick anymore and her daughter, Amy is erased from existence and it sheds some light that Lucy's biological father is not Henry Wallace but Benjamin Cahill. In the series 1 finale, it is revealed she is a member of Rittenhouse as well. 
After getting fed up with Carol protecting Lucy, Emma kills both her and her grandfather, Nicholas Keynes. With her dying breath, Carol apologized for taking Lucy's sister away and for not introducing her to Rittenhouse earlier (which is something that disgusted Lucy)
Carol is portrayed by Susanna Thompson, who also portrayed Moira Queen in the Arrowverse.