I would second getting the police involved. First, it's theft. Second, it's theft of a device you, a blind person, need to navigate the world safely. I would explain that to the police. Also ask them what your rights are as a blind person being abused in this way by a caregiver.

If you're in McDonalds, are you able to order a cane using your phone? McDonalds won't be blocking the sites.

For your O&M lady, you should try to climb the "ranks" to find her. Like, call the organization she's with. Explain your situation, tell them her name and details of where she works or her title, and keep at it until they give you another place or department to call. I don't know what O&M is, but I'm guessing that they will have resources for battling abuse of someone who is legally blind, like you.

It seems by breaking your canes and then forcing you to give her money to buy a new one, she's engaging in financial abuse of you. I would think that would be something actionable, the financial abuse, on top of the theft.

Alternately, you could go to the local media, or threaten to, if your mother doesn't replace it using her own funds. Of course, knowing abusive Ns, you would want to consider this with caution. Some Ns will back down if publicly shamed, others become violent.