My crazy ex friend won’t leave me alone!

I don’t know what to do anymore, I had a previous friend I considered a sister, we’ve known each other since 1st grade. We’re now 25. Over the years since I’ve started my first serious relationship she’s been absolutely horrible to me. I’ve been ignoring her for almost 2 years but in her mind she somehow still thinks we’re friends.

I’ve told her before to leave me alone but she still messages me, my friends, and family asking about me. And even if I block her she’s used other numbers to contact me before.

Should I continue ignoring her or ask her to leave me alone again? Has anyone been in this situation before and how did you handle it? Cause I don’t know what else to do.