I haven't heard any talk about the new FM2 chipset, but I doubt much will change besides new pin layout to support Trinity APUs.
You can draw some predictions about desktop Trinity based on any mobilie Trinity reviews out there that include Llano. You can then extrapolate those percentage gains on top of current Llano desktop APUs.Tech ReportTomshardwareAnandtech
Trinity is a progressive step for AMD (not a game-changer), but you'll have to decide whether or not you want to wait until August to buy a desktop Trinity APU or if Llano is enough for your mom. Also, by that same time, dual core Ivy Bridge CPUs will be out and still be smothering AMD on the CPU performance front while starting to catch up in IGP performance with HD4000 graphics. It will all come down to pricing and her intended usage.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 120 GB Vertex 3 Max IOPS, 2 TB Samsung EcoGreen F4, 8GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Samsung SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case