If my ex girl friend cheated on me 3 times is she worth going back to? Even if its in two years?

okay this girl i was with had at the time just moved to town and instantly i saw that she was different...i liked her and so we hung out and got to know each other...after a few days of that i asked her if she would like to be my girl friend so we could do things with each other besides talk? she said yes so we were together 2 maybe 3 days and she cheated on me with this guy who we both know and i didn't find out until 4 days after this happened and she didn't even tell me i had to here it from a friend. so i was calm and i went to talk to her she explained to me that being the new girl and having boys want her makes her fell special and she liked it but now she knows that she is with me and it will never happen again...so i was irritated but i accepted that answer and let it go...we were dating another 2 months or so and we had fights here and there just like in every relationship. so it was right before Christmas break and i decided that for Christmas to her i would give her sex...so i talked to her about it and she seemed fine but it was her first time and it was for me as well. i was confident that it would be amazing...so i had it all planned out i was staying the night at my buddies the night before and in the morning he would take me over to her house after her mom left for work because i couldn't drive and her house was empty. so i went over and we did it and then we were fine...for a week...she said was going back to her home town to visit her friends and i didn't think anything of it...because she had done it before...well this time she hung out with her ex which she was not over...and she cheated on me...she tells me and i was crushed i felt like every thing she said was a lie and all the time i spent with her was a waste...we broke up for about two months and we both dated other people in that time...she dated her ex...and she had sex with him within that time...and i dated a different girl we didn't do anything but make-out...i got back with her and every thing was great for almost 7 months...we often talked of the mistakes she made in the past and i could tell that she wasn't proud of her mistakes and she promised me that they would never happen again...then summer came and i was moving away for school and so was she...we promised each other we would see each other in about a month...in under two weeks of summer she cheated on me with her ex and i was heart broken because i loved her i really did...i told her when i see her next i was not going to be mad or mean and that she would always have a place in my heart...so we stopped talking for about a month and with in that month i found someone else who i am currently with...however here is the hard part...my ex got sick real sick and she and i started talking again she tells me she loves me and i say i love her too...she left her ex and dude she cheated on me before with and ex from all the way for when she moved to my town just so she could be with me again in two years after high school...she told me one night that she will have to have surgery again because she got sick like this once before when she was little...so i thought oh okay i will see her in the hospital. but then she said that she might not wake up after the surgery and that right before they put her to sleep she wants me to hold her hand and look her in the eyes and tell her i love her...she said if she never woke up that she would be happy in death because i was the last thing she ever saw and that i loved her...and now my heart is telling me yes she needs you go back to her she has changed in which she has and i can tell when i talk to her...but my brain is saying no remember what she did before and how bad it hurt...i really do love this girl and i still want her to be my girlfriend but i don't want it and i feel that her possibly dieing if i was to say no i don't want you that she would give up and die...then i would be haunted by sorrow and guilt for the rest of my life...Please help me all my friends say leave her behind but they are not in my situation and have no idea how hard it is.