My purebred is turning out to look moe and more like some other dog...?

I purchased my first own puppy from a popular small dog store. I went in looking for a pomeranian but fell in love with what supposedly was a miniature dachshund. The lady showed me pictures of her parents and paperwork and assured me that she was pure, so unfortunately I trusted her and paid a the full amount for a purebred mini dachshund ($500).

Through the first year I noticed that she wasnt as plump and stubby like a regular dachshund, but thought nothing of it cause she still had a lot to grow. Eventually her legs wouldnt stop growing and is now the length of a chihuahua... My sister kept telling me "oh she has a really big forehead kinda like a chihuahua face.." I have taken her out and every time someone is always like "Is that a dachshund?" One man even told me he was sure it looked like a chihuahua-dachshund mix... She's two years old now and no she is not getting a longer face and her legs are long and her body is not getting longer horizontally either... She's been apart of the family when I brought her home, so I dont plan to abandon a family member..but I dont feel like I should have paid $500 for a mutt. I could get a two mutts for less than half that price. Not only that she has had some severe illnesses and shakes like a chihuahua... I'm thinking that she has at least 1/4 chihuahua in her blood...The other day I was at petsmart and saw a lady with a dachshund and was like "Aww how cute. I have a mini one." and she was like "Oh this is a mini..." I asked her if it was a male, but it was a female... the same age as mine... My dog walked next to it and she looked like a mutt :I

I have all the paperworks saved for my dog also "AKC" paperwork which is some bs. What should I do? I want to keep her because i've already but thousands of dollars into her medical and other necessities...and she's part of the family...Please dont be rude because everyone does stupid **** and I'm sure you've all been scammed before.