The details say it is 13 inches wide but I measured mine which I got on this site and it measures 17" wide. Is this a mistake in details?

It is completely inaccurate description. Mine is 17-18" wide and I'm returning it. Way too big.

Has anyone washed this bag in the washer successfully? And, if yes, how? Thanks.

I have several Baggallini bags and have washed every one. I wash them in the gentlest cycle in my washing machine. I use either Dreft or wool-lite...or something for delicate items. I then hang dry it ....and have never had any problems and I feel better with a clean bag! As you know...we set our bags down in so many locations...and many are not clean....this option seems a purse requirement for me whenever I shop for a new purse/bag.

Is the material a canvas kind of material? Or is it like the slippery cheap nylon? Also is it strong enough?

It's not canvas. It's excellent quality very strong, not cheap slippery nylon at all . I have been using it for months now and still looks new.

Will the bag stand upright when empty?

If you want more structure to the bottom of a bag, try cutting a piece of plastic, or even cardboard to fit the bottom. When you fill the bag it will have shape and stand up. If I use cardboard, I cover it with cloth for a nice look, and can remove it for storage. I like soft bags because they are lightweight and great for storing, or stuffing into a suitcase.