Oh, no... Buffy's about saving innocent people. She's the good kind of Superhero who thinks that kind of stuff through. [ If it sounds like she's proud of her sister, she is. But a lot of this she wouldn't tell her sister to her face unless the situation were dire. Like Buffy needs that kind of ego boost. Psshh... ]
But really, that'd be awesome to learn. I know that if you have an affinity to magic sometimes you can do the simple things just by saying the words.