In terms of a light weight cruiser, a Suzuki Maurader 250 is available, but I would strongly suggest that she test ride one first. It does not instil confidence in picking up speed at anything over 60 km/h. On the plus side, it's seat height is quite low in stock configuration, which makes flat footing a possibility for the smallest of riders.
Pro's:
Cheap as hell (I believe we sold the '07 for $1500)
Low Seat height
Slimline cruiser
Very forgiving
Cons:
Lacks power
Sounds like a sewing machine (subjective)
Might make a great first bike, where you won't take a bath on the resale. But if the intention is to buy and hang onto, then I'd go with Meme's suggestion on the Harley 883 - great bike with plenty of customizations to be had!