Risks when bringing in a privately paid caretaker

We have my mom in a board and care home. She has Alzheimers. We'd like to supplement the care she gets, by bringing in a compaion a few hrs a week. The companies that provide this service are expensive ($20/hr), and require a minimum hourly visit (3-4hrs). So, we'd like to pay a private person under the table, to come in and befriend our mom, take her on outings, etc. What are our legal risks? Example: if the companion falls at the Board and Care home? If mom injures the compaion via the zheimers aggresive behavior mom has at times?