At the risk of sounding blunt ...

This friend IS NOT A FRIEND!

She is playing you and your therapist for a fool.

You need to ditch NOT A FRIEND immediately!

You need to TELL your therapist what's going on!

If your therapist still insists on keeping you both as clients, then I'd find another therapist!

Consider it a lesson learned and NEVER allow anyone to mess with your process EVER again!