Here are a list of current DVC resales via The Timeshare Store.
http://www.dvc-resales.com/dvclisting.cfm
For points at a DVC resort in Orlando, prices direct from DVC start at $130 pp for Saratoga, Old Key West, Boardwalk, Beach Club and Wilderness. $155 at Animal Kingdom, $165 at Bay Lake Tower & Grand Floridian. All of those are based on a 100 minimum point buy-in. Since your mom is not a member, I would think she'd have to buy this minimum unless they're willing to waive the minimum. But of course, less points means fewer trips.
In resale, Old Key West points are routinely in the 60-70$ range
Animal Kingdom & Saratoga routinely seem to go in the 75-90$ range.
Boardwalk & Wilderness tend to go in the 80-90 range
Bay Lake & Beach Club Villas tend to be in the upper 90s-low 100s (even though Beach Club is older, the location and Stormalong Bay make the points fetch a premium).
Grand Floridian, the newest resort (so most of those sellers are experiencing buyers' remorse but not to the point of dropping prices yet) tend to be in the 130-145 range.
So compared to buying direct from Disney/DVC, the savings could be anywhere from $20ish per point to half the price, depending on where you buy as your 'home resort."