Yes, could change wheels to something lighter and wider. Silverback website lists rim internal width as 21mm which is very skinny. Wider rims increase the tyre volume, which means you don't have to pump it up as hard. Softer tyre is more comfortable to ride and gives better traction. Feels better. Does your wife find the bike too heavy when lifting it or does it "feel" heavy when riding it? This is a very entry level bike and thus a bit of a boat anchor. You can get the weight down by changing lots of components, but can't change it's mass significantly without spending lots of money but can change it's perceived weight. Some suggestions: Check sag and rebound in fork and shock are correct. Standard handlebar width is listed as 780mm. This is very wide especially if your wife doesn't have very broad shoulders and long arms. Trim it down, it's aluminium so a regular hacksaw will do just fine. Serious. Try 740mm. Does your wife like the grips? Maybe try some different ones, in a colour she likes. Don't have to use the stuff the bike came with. Are the handlebars aligned correctly, not rotated too far up or down? Check seat height and position - think about investing in a bike fit, especially if your wife is doing frequent and longer >1hr rides. Are gears adjusted - no skipping/slipping or hesitancy when shifting. Clean and lube the chain. Are the brake and gear levers at a comfortable location. There are many small things you can do to make a bike feel nicer for little or no cash.
