Amtrak lets passengers with disabilities ask for changes to its usual rules when they need them. Ask at least 72 hours before you leave, and say clearly what would help; Amtrak answers within 72 hours. You can also ask any Amtrak employee on the spot.
“Customers with disabilities can request reasonable modifications to Amtrak policies, procedures and practices, when necessary to allow the use of Amtrak services.”
“Passengers should make their request as far in advance as possible, but no later than 72 hours before departure, and clearly describe what is needed.”
“In instances when it is not feasible or practical to make a request in advance, customers can request an "on-the-spot" modification to the policy, procedure or practice at any time to any Amtrak employee.”
If Amtrak can't do what you ask, Amtrak says it will take other steps to help, as far as it can.
A companion isn't required. But Amtrak crews don't give personal care like help with eating, dressing, medicine or the bathroom, so anyone who needs that must travel with an attendant.