you dont know how she looks. Im assuming she looks like a standard 14 year old today, which is, about 18 or up. And even when youre not thinking with your penis, its hard to figure out the age of a girl, and if she says she is a year or two above the limit, it would be stupid to ask for proof. -.-
IDK have you really never had an exchange with a girl. it never works in the "business" way you are imagining it. You dont look at documents and sign contracts. You go with it and if you hit it off, great