Looks like you're pretty much going to have to start over with taming your chinchilla. She is still growing and really needs unlimited access to food and hay or you risk health problems down the road. As far as being a terrible pet owner I don't know of any pet owner who has not made mistakes or has always been in a position to give their pets optimal care all the time. As far as being a terrible person, that's between you and God!
If you can't commit to caring for chinchilla so that it stays physically healthy then it's better to find it a new home but a chinchilla can do pretty well with a minimum of human interaction. If you don't socialize her often enough you can expect her to act wild like that and the behavior will become more engrained over time until you'll have an animal that is useless as a pet. Not being consistent with food or hay will have behavioral impact as well.
At this time don't try to touch her or remove her from the cage unless she comes to you. If you open the door to the cage and be still eventually she will get curious and come. Do this several times a day and try not to bother her when she is sleepy during the day.
You can start by trying to scratch under her chin which most chinchillas respond to by turning their head to the side and presses in for more. I think it's some kind of grooming reflex and it helps if the chinchilla is not overly skittish. Otherwise you might have to find a place to scratch that (like on the nose or between the eyes) and progress from there.
Another thing is to give a dust bath (Which should be given no more than every other day) and that has a relaxing effect as well. Treats are helpful if used in moderation. You may know that more than two raisins a day or equivalent volume of dried fruit can cause digestive problems. You can chop raisins into smaller pieces. What you don't want is your chin to come just because you have food. You want your chin to be interested in you being there.
One thing that helped when I had a wild chinchilla was to close myself up in a shower stall and him run around in there for about 15-30 minutes a day and tried to break him in gradually to tolerate being touched and held. He was not handled regularly at all before I got him and it was over a month before I could hold him in my hands for more than 20 seconds.
Remember to be deliberate and consistent and avoid movements that can startle the animal and do not reach down from above if you can avoid it. Chinchillas are prey animals and instinctively avoid that. Over time you will be able to pet her back but only after she trusts you again.
If you do it right you should see daily improvement and should be able to handle her in a couple of weeks. Since she has already proven to have been tame you should be able to regain what you've lost but that but it still can take some weeks. If you progress too quickly it will make her fearful, but if you progress too slowly you will not see improvement. Also keep in mind that female chinchillas sometime will spray urine if they feel threatened. If that happens my recommendation is just to not back off suddenly because that will reinforce that behavior. I had a male that sprayed (which is unusual since they are not built for it) and he would pee on the floor if I ever had to corner him in a room. A female can aim a stream right at your face so be prepared. Needless to say, until your chinchilla is comfortable around you, don't let her out into the room or put her in a position where you have to corner or chase her.
I am confident this will clear up with consistent work.