The Unknown is a good first title- not too long, and a haunting film with a very effective modern score. I also give another vote for Pandora's Box. If she's into the stranger stuff, point her in the direction of Daughter of Horror. Not from the classic silent era, but worth viewing. Makes for great late night fare. Man With A Movie Camera is also a lot of fun, though it has no real plot or actors.

One of my favorites is The Cabinet of Dr. Galigari. Very atmospheric and creepy, with amazing expressionistic set pieces, and an amazing ending. Especially recommended for fans of horror.

Caligari on Image or Kino... it's probably the hardest DVD choice.

DITTO!!! Great silent classic!
Also votes for 'nosferatu' and 'metropolis'

Wow, some excellent recommendations here, quite a bit more of a response than I expected, and clearly an indicator of the genre's continued vibrancy. My main goal was to express to her that the silent era was just as mature an art form during the silent era as it is now, and I think many of the titles offered here will do that easily (except for that guy that suggested the "mute" button! ).

As important a film as "Birth of a Nation" is historically, it was not an option for me. I'm black and she's white ("Hey, how about a civil war epic where the Klan are the good guys?!");it took me quite a while to come to terms with BOAN myself as a film lover.

She loves romantic films, so Sunrise was an easy choice, but I've also decided
to include City Lights for it's comedy, romance and cinematic brilliance - if that last shot doesn't get her hooked then I don't know what will! This might sound like an obvious double bill, but I think in the end these two titles will show her much of what silent cinema has to offer, and leave room for more if she so chooses. I thank you all for you help on this, and will look to this thread again if the above sparks an interest in her.