From further research I learned that the reimbursement of expenses is in fact considered rent. Also, my mother paying all the expenses directly is no different than her paying rent to me. Lastly, her payments cannot be considered a gift as she is getting something in return for them. Thus, I consider the first part of answer 3) of PatriciaV to be incorrect.
3) Reimbursement of expenses would not be considered rent as long as the activity was not an intent to make a profit. As a second home, you would be able to claim mortgage interest and property taxes, but no other expenses.
I am happy to be wrong. Actually, I wish I'd be wrong, but unless somebody is able to proof it with a tax code reference, I will have to continue declaring my mom's payments as rental income.
