The following is based on my last visit. Things may have changed... as things are always changing at WDW.
She may experience difficulty.
When you arrive at your resort for the 1st time of your stay, you will get stopped at the "guard station" (at the entrance to the parking lot your resort). The guard will ask for your name to confirm that you are allowed to enter the parking lot. If your name is on the list of people expected, the guard will permit you to enter the parking lot. At check-in you will be given a "parking pass." Which is an 8 1/2 x 11 piece of paper that has your resort, check-in, check-out type info. If she does not have the resort supplied parking pass they will stop her at the guard station. Without the parking pass, the guard might not let her enter the parking lot.
Once again, this is how it was on my last visit about a year ago, the process may have changed...