I am so sorry to hear you are going through this right now. It's hard enough being a nurse- you don't need this from a parent.
I had an incident a couple years ago where I called CPS on a child, and it was a justified call (I was catching the tip of the iceberg- offending parent was removed from the home about a month later after a second call was made). Due to the nature of the call, I did not disclose my contacting CPS to the family.
The offending parent was VERY upset that CPS had gone out to the home, and he and his girlfriend were repeatedly calling my building, asking to speak with the nurse, at one point even hanging out in the parking lot during drop off, I guess looking for me.
I refused to meet with the family alone, and definitely not before I had followed up with the CPS worker. Once I had a CPS update, I met with the parents and had two other staff present. Honestly, I don't know how any of us would have gotten through that meeting alone. Some staff were skeptical of my requesting assistance, but the way I see it, if a parent is unstable enough to harm a child, who knows what else they might do?
Long story short, establish your boundaries with this woman yesterday. If she comes into your office alone, step out and get back up. Meet in an area with others present. Just please do not be alone with her, for your safety and your sanity.
Also, if admin hasn't done this yet, consider a staff meeting with mom where school rules and state law re: CPS calls are reviewed. The meeting should NOT be a time to out the staff member who called CPS- this woman does not seem like a safe person to be disclosing that info to. And anyways, mom should be getting the message that child safety is a TEAM effort, with all staff supporting each other.