Wade - if you are based in NY why not rent? Or are you out West 30+ days a year?
A strategy that I'd recommend is on your next trip out west have your wife book a day long intermediate group lesson on a non-Holiday weekday. It will probably end up being herself and maybe a few other people in the group (I often find that the most profound learning takes place in smaller groups of like ability). It may be that an instructor will unlock something that is / is not happening with your wife's movement patterns that will allow her to ski more efficiently.
90 underfoot, in her current ski, seems like plenty. I'd classify a 105 as a full-on pow ski suitable for mainly heli or cat skiing. My go-to touring ski is 95 underfoot and my widest front side ski is 82 underfoot. You could purchase that new ski for her, but what you will likely find is if she does unlock efficiencies (though chance or coaching) and becomes a stronger technical skier she will gravitate towards narrower skis, not wider.
Enjoy.
Thanks for your response, Marty.
We do 10 to 13 days skiing out west each year. I thought I might pick her up some wider skis given she enjoyed them during the massive powder week we just had in Utah.
Perhaps I'm underselling my wife's ability. She definitely doesn't need an intermediate group lesson. She skis very well, and skis in steep, difficult terrain - she just doesn't like to ski as quickly as I do (she's clearly smarter than I am). We've had a couple of private lessons with
@Bob Barnes and usually take a private, or some type of advanced / expert small group lesson when we travel. We both enjoy challenging ourselves and both enjoy working to improve our skiing. By way of an example, some of the more rowdy stuff she's enjoyed skiing on our last few trips has included the Deep Temerity trees and Highlands Bowl at Aspen Highlands, Hanging Valley as Snowmass, STH and Berry Berry Steep at Snowbird, and a few of the steeper lines in Catherine's Area at Alta. She's also very happy to ski mellower off piste lines, and will ski groomers if that's what the group is doing, but groomers aren't really what she enjoys skiing.
I ski a 108 waist ski as my go to western travel ski, and I find it works pretty well on firmer snow, pretty well in full on powder, and it excels in between those two extremes in the soft left over snow and crud we wind up skiing most of the time when we head west. It's entirely possible that 105 is wider than she "needs" for the type of skiing we usually do when we travel, but I think for her style of skiing, it would work well enough at either end of the conditions spectrum, and like my skis, I think she'd enjoy it more than her current skis for all the in between days.
We could definitely rent skis for her if the conditions warrant it (we did that on the last trip), but if I can find something that will work well for her at a good price (say, <$500), it'll just about pay for itself in one trip. Hopefully something will pop up in the end of season sales that will fit and that she'll enjoy skiing.