It's hard (for me) to give you an exact date on that vacuum. The plastic body vacs with tool storage on top started out being called the Epic 6000, in blue with ivory trim and steel wands. This was around 1992. A few years later, Electrolux added plastic wands and changed the name to the Epic 6500, still in blue. Then the color was changed to all gray (still an Epic 6500) to match the all-new Reniassance, which had replaced the last metal body 1251 canister. At some point, the Epic 6500 changed colors again, to a white body with gray trim (not the same as the recent Aerus of the same color scheme). This color is the hardest to find, at least with the Electrolux name on it. The final color combo to wear the Electrolux name was the white body, blue trim Epic 6500. This model was sold in the very late 1990s/early 2000s just prior to the name change to Aerus. The color scheme matched the updated Reniassance, which was renamed thd Guardian. When Electrolux changed named to Aerus in about 2003, the Epic 6500 was renamed the Lux 7000, but the color combination of white body, blue trim remained. Shortly after, Aerus changed the name to Lux Legacy and still kept the blue/which color scheme. This is the vacuum you've posted about... it should be about a 2005ish model, or roughly 7 to 9 years old. After "your" vacuum, the Lux Legacy was recolored with a white body and gray trim, almost identical to the earlier, short-lived Epic 6500 color scheme. Finally, the Lux Legacy was recolored to a black body, dark gray trim in 2014 for the 90th Anniversary.
What does all of this mean for the price of your vacuum? Well, not a lot. The price she's asking is near the top of what you'd see a Legacy/Epic sell for. Typically, the white/gray Lux Legacy models under the Aerus name bring the most money ($400-500) because they're nearly new. The early blue body Epic 6000 and 6500 models ($200-300) typically bring more money than the newer all gray 6500s ($100-300), probably because the blue color is so unusual. The white/gray 6500s are rare, but they usual bring the same as the blue 6500s ($200-300). The white/blue machines (Epic 6500, Lux 7000, and Lux Legacy) all go for the same price ($300-400), usually a little more than the blue 6500s and a little less than the white/gray Lux Legacy.
So yeah.. you're not getting ripped, that's for sure. It's priced right. If it was me, I'd care more about the looks, and I'd go with either an older blue older 6500 to save some money, or a newer white/gray Legacy to ensure it spent as little time as possible in the hands of someone who maybe didn't maintain it well. But they're all good looking machines. Except the all-gray ones from the mid 90s. Gross.