How do I deal with this ex colleague/ best friend?

Me and Hayley were very close friends for years — we worked together and spent loads of time outside work. Things changed when another colleague, Chloe, started spreading false rumours about someone at work. Hayley and I both told Chloe to stop, but when she was confronted, she blamed me and Hayley for starting them. I cut Chloe off, but Hayley chose to forgive her and started seeing her behind my back, which really hurt and caused a big rift between us.
I moved on, made new friends at work, and things in my personal life improved. Hayley became distant and started making passive comments. Later, she told me she planned to kill herself. I took it seriously and reported it to a manager under duty of care. She was investigated and support was put in place, but she blamed me for it and our relationship completely broke down after that.
She was later dismissed from the company. Recently, she returned working for an external agency in the same workplace, and since then I’ve suddenly had repeated issues raised against me that I’ve never had before in five years — with her name on the paperwork. Given our history, it’s made things uncomfortable and concerning professionally.
Updates
5 mo
she's not a very nice person inside and out and is known to be jealous, spiteful, bitter and has no shame about lying
How do I deal with this ex colleague/ best friend?
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