oh, you sound exactly like me!!! i also love louisdog and have a few of there things but not many. another very nice brand is Oscar Newman ( lol. not sure if you have discovered that one yet but they are gorgeous also) too bad i can not get them at low price like the ruff ruff.
i would recommend just ordering one or two or a just a few to see how the fit is. you may find they are too roomy but like i said before , i think the XS is going to fit better on your girl than the XXS.
no rush. let me know whenever you'd like which ones you want to order
