What's your reasoning for wanting papers if you're not going to breed her? To show her in obedience or agility perhaps? If so, you don't need a pedigree to obtain an ILP number.
Go to akc.org and surf the site for an ILP application. It'll have the instructions on there like: writing up why you believe her to be a purebred Chihuahua and what pictures you need to submit and at what angles.
I'm sure you'll get your ILP number and THEN you can compete!
(she'll have to be spayed before the number is given to you though, since you're not interested in breeding, that shouldn't be a problem for you....it'd be the only obstacle I can think of...)