I don't see what will make the bike very heavy. Yes its steel, but if its a couple pounds heavier than a GOOD aluminum bike, that just wont be noticeable when riding. The reviews site claims it weighs 25 pounds. You will be hardpressed to find something significantly lighter that is also in good condition and a quality bike for $300 or less.

The gearing should be great for a beginner since it has a triple front. She will be able to get some low gearing to make any hills easier.

As for a bike weighing 1/4 a person- you really aren't going to get a bike for $300 or less to weigh less than 22# or so(this is a generalization, not some hard line truth).
Weight would be down on the list of concerns for me. Fit and comfort would be the highest followed veryclose by overall condition. The bike has RSX components- from what I have read and seen these are fine and are reliable if taken care of.