Generally, good advice however, I'm fairly petite and was 12 (maybe 80 lbs) the first time my father taught me to shoot the 12 g. I might even fit in the granny category as well....I like my 12 g. My view is that if you are taught to shoot correctly from the start, we "petite" ladies can handle most everything. I've even used a couple of different 50 cals and hit the target on the first try.
Training ladies, and then more training...with everything you can get the chance to learn to shoot! You just never know what you might end up having to use WTSHTF.