Have your friend goto several sewing machine dealers, shops... and 'test drive' the newer machines. She'll soon get a feel for which company she does/doesn't like.
Also have her do a list of what types of sewing she already does... and what she 'wants' to do. From that, figure out what features she MUST have and what features she WANTS.
Then start looking on Craigslist, local papers, local sew shops, and local ebay for what is being sold and for how much.
From all of the above, she can make a list of which manufacturers she likes, which models (used or not) that have the best of the features she wants, and all the features she Needs. Search the ads for used machines, cross off those out of price range.... buy.
Remind her that she needs to find a local sew shop/dealer to service and repair her machine later. Best to find a dealer she likes now. Dealers will sell used machines, refurbished and cleaned up. They're usually more expensive, but they are ready to sew and don't need service.
A lot of sewing is personal preference.... it's what she likes... Good luck and happy hunting. There WILL be a machine out there for her. Perhaps once she knows what models she wants... you could post a want ad on this site, asking for anyone local to her, that has one of the listed machine... who might be willing to sell it to her for less. Worth a shot... <smile>