Helen pauses again, her eyes taking in Rebekah for a moment. She has no reason not to trust her, but at the same time, it's a sensitive subject and not one she particularly wants to go into too many details with at the moment. Even so, she can offer at least part of the truth.
"I don't normally use it, as it's difficult to explain why someone who has lived from 1850 to 2011 is 274 years old."
And the answer brings up more questions than she likes, questions about time travel.