DC shoes?!? please hurry and help!?

So i orderd DC shoes. they are kinda like my moms, my moms feet are smaller then mine, and her shoes are a size 7, and i can fit my foot in there, but its just tight. and my puma running shoes are a size 8, so i orderd a size 8. anyways... what happens if they dont fit right, can i send them back online or what?