Wow it sounds like you're in the middle of a really tough situation OP!
I would actually keep a diary of dates and times of interactions with this student that could be problematic, if there are no interactions that you think would be a problem then take note of this also. Write down names, dates, other students that are witnesses.
Don't blame yourself! Sometimes these things happen regardless of how hard we work.
Tell the other teacher if you trust them. It's important to have support and someone to understand what you're going through.
Be proactive about it. Participate in workshops with the student and their mother in order to work through these issues. The child who is telling these lies should be 'comfortable' in the presence of their mother to tell their mother what you've been doing with you there. Address the issues immediately. Show the mother you are willing to cooperate and want this resolved.
Meet with the mother and tell her that attacking you is not appropriate. Let her know that what she is saying and doing is unacceptable and won't be tolerated. If you're afraid have the other teacher there to support you.
If you're too scared to confront the mother then take it to your local union, district or professional association.
I found a website that says the following:
Dealing with Harassment—Steps to Take
- Don’t try to handle this alone. Seek the support and assistance of your principal.
- Make every reasonable attempt to meet with the parent. Ensure that your principal is present.
- Require that allegations or complaints about your actions be detailed and specific, not vague and general.
- Listen carefully. Try to understand the parent’s perspective. There may be an element of truth in the concern being expressed.
- Try to elicit the parent’s help to reach a satisfactory resolution. The goal is to resolve the problem.
- Keep an accurate written account of events, times, places and, whenever possible, the names of witnesses.
- If the harassment persists, request, in writing, that school or district administration become involved. Employers have an obligation to protect their employees.
- Contact your Association! You are entitled to advice, assistance and representation.