As I stated, you need to be doing a banishing ritual to get her out of your life, not just shielding yourself, which, from what you describe, seems to be ineffective.
Pick up a copy of Magical Protection by Damon Brand, and learn his Sword Banishing. It’s simple, and quite effective from all reports. There are also rituals in there for protection against stalkers, bullies, and unwanted attention, everything you have described this person as doing.
The Gallery of Magick books are simple and don’t generally require a lot of skill or time to work. You can also chant the archangel Michael mantra I posted: