Think his SO is on the verge of stalking

Hi! Hope someone can offer some insight/suggestions. Its one thing for his SO & me to drive by each other & she gives me a dirty look...I deserve that...BUT...this past week she has been driving everywhere I am..sometimes 2 or 3 times a day. Today, I was meeting a friend for lunch but had to make a quick stop at my house. As I was driving away, SHE drives by me...my house is definitely out of the way for her, so I believe she is beginning to follow me. I have been told I should start keeping track of when, where, & how often we keep "running" into each other. I also have been told that she is phoning ex MM at the place he is staying & then hanging up...she does this several time. I do not want him to think its me. I swear she is losing it. Any suggestions? Has anyone else here had this problem.

Cin