not very spur of the moment, but as anya mentioned, there are the implants...
there's also a female condom, but i don't know anything about that (whether it's mass marketed or if you need a prescription to get it)...
there's the unreliable rythym method (don't have sex when she's most fertile, which isn't as easy to predict, but ovulation predictors that people use to get pregnant might help reduce the odds)...
either way, the best method of not getting pregnant is abstinence, after that everything else has it's risks...
i hated the pill too, so i can see where she's coming from... when i was on it i did find a low dosage one that i tolerated well... it was called aleese i think... very mild, didn't make me a hormonal mess (well, no more than usual)... maybe discuss her concerns with her doctor and see if they can come up with a better option...