I'm of the mind that maybe she just didn't hear you. Did you notice if she was wearing ear buds (never a good idea if you are riding on busy roads)? But anyway, I guess it is possible she was just a rude person or just wasn't feeling social.
I've had my fair share of experience with rudeness too. I remember when I first started riding roadies. I was out for a spin on my ole trusty steel frame Trek 400, toe clips and friction shifters on the downtube and rocking a 5-speed freewheel. There I was decked out in cargo shorts and a t-shirt just cruising along. I came across not one, but two small groups of riders during my ride. I waved both times... and not a single wave or acknowledgement of my presence either time.
Now, fast forward a year to when I got my Trek 5500 and started wearing lycra shorts and jerseys, and wouldn't you know it, the waves began to be returned. Coincidence? I think not.
Don't let it discourage you. Just keep riding for yourself and don't worry about the snobs out there.