Either walk her home or call her a taxi. She is your girlfriend. Some people don't like the "your" part of it, saying it connotes possession or other ugly words, but that's beside the point. There is now some responsibility on your part.
Think of it this way: You're sitting here trying to figure out whether or not you should escort her home, and decide not to. On the walk home, alone, she gets attacked. You find out when she calls you from the hospital a few hours later.
Does that help you make your decision?
I feel responsibility but I know she's travelling and walking home from work at night too which I don't like. Are you talking about dates?
Weren't you? You can't help it if she works at night and walks home alone, but if you ask her out, she's your responsibility until she's back home safely.
Obviously, however, my views are pretty different from most others in this thread. I know two women who have been raped, both were attacked while walking alone at night, and I don't consider it a topic open for trolling and joking around, but that's just me. If you're fine letting her walk home alone at night because women are "almost never" attacked, or because more women are supposedly assaulted by acquaintances than by strangers (although I don't see how that makes walking alone at night any safer), then by all means, let her go. Where I live, there's no question of "if" it will happen; the question is "when".