As long as you understand that if you can't try it on her actual foot there is no way you'll know the right size or width and it probably will be one of those things where you get it, put it on, doesn't fit, send it back for another size, get that pair and they fit totally different and still not right, so send that pair back to exchange it for an even different pair....etc.....
Ordering online for something like this is very frustrating and time consuming. IF shoes from Target and other general places do not fit there is little chance of finding an online shoe that will fit any better.
Look up some other places in your area that sells only shoes. You can take a day and drive to some different malls or shopping centers and just try on shoes all day. It could be a totally find day for the both of you.
Most moms get their kids shoes at places like Target or Walmart and then put a heavy sock on them until their foot grows a bit then a thinner sock. This is how we all deal with having shoes that are not custom made.
Our granddaughter has a slightly narrow foot. BUT with a good sock on almost every shoe will stay on her foot and be comfortable.
She can walk in Walmart right now and just about any size 1 little girls shoe is going to fit her.
Her ballet shoes are 3's, her hip hop split sole sneaker is a 4 1/2, and her jazz shoe style tap shoes are a 2. So shoes are made in a variety of different styles and sizes and you cannot depend on what the writing inside the shoe says it is.