Thanks for your replies. I took her to petco and tried on the ones they had there. I guess she is an xxs. I didn't like the fido floats b/c her hair is long and it can get caught in the zipper. I ordered a pawsaboard brand from ebay.
The one with the nautical theme, bc you know we are pirates! LOL They are way cheaper on ebay than at petco! $20 vs $35!