How do I let my ex bestie knows im only nice to her because we work together whilst staying professional?

I fell out with my ex bestie of 3 years at the start of the year because she lied about wanting to kill herself to get an engaged man's attention. Instead of him coming to save her I did and I tried to get her help which she didn't appreciate because I exposed what she was really doing.

Instead of talking to me about this she blocked me on everything, slagged me off to everyone and tried to bully my other friends for sticking by my side.

Are friendship was already in a bad place as it was always one sided she only cares about herself and would always ditch me for others, act jealous of me and forget or not care about important things in my life like my birthday when I'd make a massive effort for hers.

I was also being stalked and harassed at this time by another colleague who got fired for his behaviour towards me and when we fell out she went running her mouth to him about me and told him my information but she doesn't know I know that because I haven't confronted her about it another friend told me.

I was okay with her and had moved on until I found that out as I find that unforgivable. I can't even stand to look her in the eyes after that. She was like a sister to me once, we laughed, cried, had sleepovers, night outs everything together and to do that is a massive stab in the heart to me.

She also caused shit between my other friends now and making everyone turn against each other now to the point the police are now involved due to someone getting beaten up because of her shit stirring.

I'm in a position at my work were I have to help and protect my colleagues which means I have to be kind and respectful towards everyone even if i don't like that person including her.

She keeps talking to me lately and today she asked me to play table football with her when I was on my lunch I said i wasn't any good at it so no but I actually wished I'd told her to stick it up her arse.

How do I let my ex bestie knows im only nice to her because we work together whilst staying professional?
Post Opinion