Hi Enchilila,
Wow, you are lucky ! A free Yorky!!!! I am so envious!!!
Just because Yorkies are small, I would get a harness, I think they are safer, less stress on their little necks.
Has your niece given her any training at all? Like a few obedience commands like sit, stay or come when called ? Is she giving you the grooming tools?
At the age of 2 and never been on a leash, she may have a problem with it. However, you are bigger than her, so you just have to have patience and stick to your rules and don't let her rule you no matter how cute she is
The following is what I have done in the past with a new puppy, I should think it would work on a 2 year old too, might take longer, just be patient with her .
First get her used to her harness, lots of choices, make sure it is adjustable and comfortable and not easy to get out of. Take her with you when you go to pick it out, most places will let you try them on her so you can get a good fitting.
Let her wear it during the day, take it off at night if you like, it will wear a place in her hair if her hair is long though, especially if you leave it on all of the time! Collars will do the same thing on the neck hair!
I would let her wear it every day,(during the day) for a few days or a week, just to get used to it. Give her lots of praises and tell her how pretty she looks. She may not understand what you are saying but she will associate it with you praising her and that its a good thing . Give her a few treats at first to get her to associate it with being fun!
After you think she is getting used to the harness, then you can introduce her leash. Just attach it to the harness and let her drag it around the house, while you watch her. Don't let her chew on it! Don't let her out of your site while she has it on. Pick it up and let her know you have hold of it, but, don't yank on it or make any moves that she would associate it with being a punishment or painful. Keep the session short then remove the leash.
Do this every day for short sessions and eventually take her for a walk around the yard or a small area in the house and let her get used to you controlling the leash and direction of the walk. Use treats to encourage the right direction and having fun while walking,calling her name each time you change direction so she will pay attention to you.
If you want to find out more about Yorkies, there are lots of books out there, I would just start picking them up and thumb thru them and make sure they are recent publishings, and have at least info about grooming,nutrition,training and diseases. Most breed specific books have this info in them. I wouldn't buy the first one you see, but do pick up several and take a good look at them. Amazon.com,Barnes and Noble,Books a Million,Borders, and places like Petsmart and Petco have breed specific books. I must own 10 different Yorky books, each one has a little different info, but I had a problem with choosing which book to get
Oh and take her to your vet and find out what shots she has had, and look into getting her spayed if you have no intention of breeding her. Just my thoughts but not being spayed and you having no intention of breeding her will not keep an amorous intact male from getting her pregnant.
Sorry for the long explanation, but hope it helps!
Abby and me