Not too sure from your post if you are here line manager or not so I will try to answer both
In the first instance try to find a connection. Despite the age you will have something in common even if in this circumstance it is that you have both held the same job. Perhaps her self esteem has taken a knock from stepping down and maybe asking her for her advice on something relating to your role could build that bridge (You don't really need her help, you could just say "I can do this but ------ you used to do it faster, how did you do it). This could provide her with self worth or it could work the other way around
Failing this I would take her to the side and look to discuss the issue, this may seem an absolutely horrid and awkward thing to do but sometimes honesty is the best policy (sometimes raising grievances can do more damage than good in working relationships).
Finally if nothing is sorted raise it as a formal grievance with your line manager (has to be in writing) if your company has a Human Resources department copy them in so they can guide the manager and stop them shuffling it under the carpet if that is what they have been doing.