I am helping a 5 year old mare than doesn't have hardly any training (she fights me to lunge and quits as soon as she decides to do so) how do I keep her attention?

If you have a roundpen use that for a bit and a lounge whip to keep her going. If she stops make her go by cracking the whip. If she turns around without you asking her to then make her do a hard roll back a few times and go back to normal. Eventually she should turn towards you when you ask and go the other direction. That's showing her respect and it's got I train my 2 year olds
(Adding to my previous comment) while in the round pen you can let the horse loose so you arnt connected through ropes. I find this does wonders for a horse that has made a habit out of ignoring and/or disrespecting you.
I have had this problem with a mare I work with. Problem is, when you start working with a horse late they usually don't like being told what to do. Sometimes you have to be firm with them (in no way am I saying to hit or abuse the horse in anyway, this can only send the horse backwards). The method that worked for me was to control the horses speed, direction and movement in the round pen primarily on the ground.
Yes, the owner taught her that if she stops she will get petted and loved on. So whenever I do try to send her off she pins her ears and rears up at me
Keep her changing what she's doing and working hard. Keep her moving and working in forward paces so that she doesn't get the chance to stop or run away. Keep her occupied with lots of transitions. When she's good make sure to reward her with walk breaks but not to the point where she thinks she can get out of work.
Show her that stopping is unacceptable. When she decides to stop, chase her off and push her harder. Change directions often and sporadically. A horse that does as it pleases is disrespectful and will soon learn that it can get away with other things too. Move her feet as often as you can.
Instead of doing one thing for a long period of time mix it up or add something in my mare is like that to
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