What is wrong with my dog and how can I help her?

her name is misty. my brother brought her home about 10 years ago, she was a stray. ever since we first got her she has had behavior problems. she nips at people ankles when they come over. she doesnt draw blood or anything, just pinches. well about a year ago i started taking her on walks and ever since then she will not leave me alone. if i go to the bathroom and leave the door cracked she follows me and just stands there wagging her tail. wherever i go she goes. even if i just get up really quick. she has become completely attached to me and u can call me mean but it's very annoying. she also will not eat anything. she eats only a tiny bit every couple days. can someone tell me whats wrong with her?