Please don't give up on her. A new horse needs time to get adjusted to new people, surroundings, new feed, routines, etc., and spending time with her on the ground just getting to know her will get you two off to a good start.
A round pen is a great place just to relax with her and build your relationship before you ask to get on her back, and when you do I would do so bareback with a halter and reins and just get a feel for each other. Without knowing much if anything about her history, there is no telling what she knows and how she's been treated, and from what you described, her trust is shot, and you have nothing if you don't have trust, so that is likely problem #1 which isn't her fault or your fault.
If the person you bought her from is a horse trader, she may have been through one bad owner after another and probably was aced when you came out to look at her and ride her, so based on how she's acting you may as well consider yourself to have rescued a horse and it's time to rehabilitate her :)
Do you know how old she is? Whatever the person told you, I would open her mouth and take a look for yourself. You can guess well by the angle of the incisors approximately how old she is.
I post this video a lot because I think it's very critical to address possible pain issues first: https://www.youtube.com/user/HolisticHorseWorks#g/u
I am not a fan of lunging, there's an art to it and if it's not done properly it is really detrimental, and can injure or lame a horse as well. As for her pulling back when she's tied, I suggest not tying her for now, you can just drape the rope over or around a post or whatnot without securing it in any way while you're brushing her and such, and if she still pulls back, then keep the rope in your hand and work with her, and stay very close to her body and be soft.
Sometimes you have to work backwards, sometimes back to Square One, to regain their trust, and you can work magic. Be her friend and ally first, and let her know you are going to do what you can to understand her and be there for her. She's probably had a hard life already, and God only knows how many homes.