My line would be something like "Hey!...You should really get an umbrella!!!" and then just continue to walk next to her with the umbrella only over myself. The hotter she is, the funnier the joke is. If she actually gets it and runs up to join you, that is the type of girl I would want to talk to anyway. And I wouldn't mind at all holding an umbrella for a girl, provided I get to rip on her the whole time. "Oh sure, get a man to provide for you, some feminist you are.
" Obviously, this is all done in a friendly and joking way. If the girl looks like she's about to start crying when you first talk to her, she didn't get the joke. And obviously if anyone needs help, you should still offer. Even if it's a little old lady. Your frame is that you're really a great guy, and that's the joke of
pretending to be a jerk.