بسم الله الرحمن الرحيم
You may visit your non-Muslim mother and help her in cleaning etc there is no harm rather it is a task of virtues and reward. Islam emphasises highly to behave parents in good way and serve and help them. You may also wash her dishes. However, you should not wash dishes in which any haram thing is cooked or eaten, and let your mother wash it.
May Allah give your mother taufiq to accept Islam! Amen!
Allah knows Best!
Darul Uloom Deoband