Truck Tractor over the road use.

Expenses, yes.

Depreciation, maybe.

In my opinion, if there is a contract of ownership between the taxpayer and the person who holds the title that the taxpayer, then the taxpayer can claim depreciation.

"someone else's name who helped her to acquire the truck"

That makes it sound like her truck.  The title is in someone else's name and that other someone actually paid for the truck with their own dollar bills?

This makes me a bit uncomfortable: "She has been paying the truck and all related expenses using her LLC. Can she deduct all the truck expenses under her schedule C?"

in concert with: "She is paying back the owner in a monthly basis."

Because it isn't clear if there is a Lease or Loan agreement between these two parties. At first, it seems like she was making the Payments to the lender, but with both parts, she is paying the other person directly.

Are you trying to write off the Truck Payments?

Is the owner of the truck considering it a lease, reporting the payments she makes as rental income and depreciating the truck (probably showing a Schedule C loss)?  This used to be a popular tax shelter, especially in the days of investment credit.