The airline should be able to help.
You could request an escort for your daughter with United Airlines and it shouldn't be a problem. They will take her to the airplane at departure and assist her with any connecting flights until her arrival to her final destination in Rome.
You should contact United and they will assist you...
I would contact the airline and get the information on the process.
Newark Airport offers wheelchair assistance. If she requires assistance you can use the United App to request it in advance or when you check in with an agent.
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