Man, I completely suck.
I think I'm way too nice. I've been feeling guilty for not contacting her. I have made a promise that if "us" doesn't work out, I promised to be her friend. She was going through rough times at that moment and she told me how people tend to leave her life.
What should I do? I feel guilty and bad the more I think about it.
That's sad, but maybe people tend to leave her life because she treats them poorly.
Good decisions come from experience. Experience comes from bad decisions.
You're even remotely thinking about sending her presents? Are you out of your mind. She treats you like shite and you want to send her presents anyway? Save the presents for the birthday of somebody who counts for something in your life. Unless you enjoy being walked on in which case I'd give her the presents, text her all the time and tell her you will love her forever.