What about a Samyang 14mm F2.8 - hang on a moment - you've got one of those. Why can't she borrow that one?
Some legacy lenses are good but manual focus.
I got a lovely Minolta Rokkor MD 50mm F1.4 with terrific bokeh. It was under $300. You need an adapter. Ebay has them. There was a thread on another site about bokeh and posting the best example and some of the absolute best of any lens were from the Rokkor 50mm F1.4 which is why I got one. It renders blues very nicely as well. Other lenses are a tad sharper but it has lovely rendering, quite unique.
Nikon 28mm F2.8 AIS is common legacy lens lusted after by the Nikon crowd. Under $200. Adapter off Ebay under $25. It has an aperture ring.
Contax G Zeiss 28mm is a lovely lens. Needs a Fotodiox adapter ($80) and they run about $450 or so. There is also a Contax G 35mm which is usually cheaper.
Samyang 35mm F1.4 gets good reviews. Comes in a Canon mount. I have the Samyang 24mm F1.4 and its a good landscape lens but its more like $650.
keh.com is a good resource for 2nd hand lenses and they rate the condition of the lens very conservatively.
http://www.keh.com/Camera/format-35m...c=81079&r=WG&f
Voigtlander lenses get good raps. There's a 20mm F3.5, a 28mm as well a 35 and a 40. They are made by Cosina in Japan the same high end lens maker that Zeiss uses to make their lenses. They are a cut above many other lenses and 2nd hand you could pick one up for around that money.
Greg.