My Mom has a public guardian and a Peaceful Contact was placed on me. Can I still visit her?

I think so. You must remain "peaceful" at all times toward her. Does she want you to visit? What does the guardian say?

If you visit, take someone with you who can keep you calm and witness your good behavior. Agree to leave if they say so. Without a witness, if mom is delusional and makes further accusations you are in deep trouble.

Call the guardian and co-ordinate your visit with them, so that they can be there or be nearby. If you can meet in a public place (like the common room or activities room of a NH or perhaps at the local library if they live in the community), that would be best.
If you are on any medications, be sure to take them as prescribed so that you are yourself at your best too. Good luck.