When I had psychosis I thought people were following me, but I soon realised I was wrong, is there any chance she could be attracted to you and just hoping to bump into you to start a conversation, does she seem threatening in any way if not maybe next time both of you see each other in a busy part of town, break the ice by giving her a compliment you soon see if its someone who wants to cause you harm.
But be on your guard it could be totally innocent but you can buy a cheap personal or wireless home alarm of Amazon and just ensure all the windows and dorrs are bolted.
Good luck I hope it turns out to be an innocent mistake.
Cheers
Geo