I Googled Fleetwood sewing machine and looked at both web prices and images. If both the machine and cabinet are in great cosmetic condition, I would pay $100 even though that is in the high end of the range for me. Online the portable versions in good condition are advertised for $100 and up, so the cabinet and accessories should add some value. This is supposed to be a very good Japanese-made machine. I haven't watched it, but here is a Youtube video of it:
http://www.youtube.com/watch?v=4dIbmgnz4_g
If advertised, I doubt your friend could get more than $50 to $75 for the machine locally unless you live in an area where vintage machines sell well (they don't sell well in most areas).
Have you actually seen the machine and cabinet? I'm thinking it's not going to be worth $100 unless it's in really good cosmetic condition. You could perhaps let your friend know that you're not willing to pay $100 for a vintage machine. If she then tries to sell it on craigslist or elsewhere, she may find that they are harder to sell than she imagined and offer it to you for less.