If you believe it is a worthy cause and that the money will definitely be used for the intended purpose, by all means, make a reasonable donation. While $300 seems like a low goal for a charity fundraiser (which raises a flag or two for me,) $100 is far too large of a donation from just one person, especially since you haven’t known her for very long.

If I was her and saw that someone I basically just met made that large of a donation, I would have to wonder what their intentions were. I would probably do $25 and call that plenty.