For cleaning purposes, actually, you could use kitniyos on Pesach. The issue is in food use, and some preparation is done before Pesach (e.g. drying romaine lettuce for marror).
Most people who are makpid probably just buy one type, not to have to keep track, but your point is still valid. In a case where money is so tight, she should have only bought the more expensive type for food (if her rav required or recommended it). She probably could have gotten away with one, maybe two rolls.