this is a very close relationship indeed.
Based on the Shared cM Project chart, your choices are:
(Grandparent is also in the cM range but not possible based on the ages)
With a 10 year difference, your top two possibilities are that she is the full sister of one of your parents (not a half sister) or your own half sister (not a full sister).
Your next steps are:
Find others in your family to test and compare them to this woman.
Your parents are best but any cousin will do.
Get her story. Was she adopted? Does she know both her birth parents? Have any of her siblings tested?
Pound the paper trail. What can you find to document your relationship? Get birth/marriage certificates, where her parents were living around the time of her birth. Anything you can find.
Good luck and please post here with an update.