What is the destiny of her sister who suffered from serious and painful diseases before she died?
Question

                My 14-year-old sister has passed away recently. And I would like to know what her place well be now as she had suffered from so many illnesses?

Since birth she was born with a rear skin disease (fragile skin, breaking very easily and open wounds all over the body) that affected all her body parts (internal external) and wish caused her allot of pain and meant that she had to have so many operations. Then on top of her birth illness (skin disease) she suffered enlarge spleen, enlarged liver, skin cancer and the final illness that she got before passing away was a kidney failure meaning both kidneys stop working complelty. After her kidneys stopped she lived on the dialysis machine for four month going through so much pain and agony every time the machine was used which was every night. Her death was a sudden death and doctors said it was that her body had just given up.
Praise be to Allah. 
          It is part of the belief of Ahl al-Sunnah wa’l-Jamaa’ah 
          that we cannot state definitively that any of the people of the Qiblah 
          (i.e., Muslims) will go to Paradise or to Hell, except for those concerning 
          whom Allaah or His Messenger have testified, because testifying to that 
          effect concerning any person is something that can only be known via 
          wahy (revelation), and revelation came to an end with the death of the 
          Prophet 
          
          (peace and blessings of Allaah be upon him). So no one knows in what 
          state people will die, or what is hidden in their hearts except Allaah 
          Who created them. But the Muslim who believes in Tawheed will inevitably 
          enter Paradise if he bears witness to the Shahaadatayn and fulfils the 
          duties they require. Allaah may punish him if he commits some sins, 
          or He may forgive him, but his ultimate destiny will be Paradise. We 
          have to believe in Allaah’s promise which gives these glad tidings. 
 
          It was reported in the texts that if any Muslim child 
          dies before reaching the age of puberty, he will be under the care of 
          the Prophet of Allaah Ibraaheem (peace be upon him) and his wife Saarah, 
          and he will intercede for his parents on the Day of Resurrection. 
 
          But the one who lives beyond the age of puberty will 
          be requited for his deeds; if they were good then he will be rewarded, 
          otherwise he will be subject to the will of Allaah: if He wills He will 
          punish him and if He wills He will forgive him. 
 
          What the questioner mentioned, of the suffering endured 
          by her sister – may Allaah have mercy on her – perhaps Allaah will raise 
          her status with Him because of that. For no distress or grief befalls 
          a believer but Allaah expiates some of his sins thereby. It was reported 
          in the ahaadeeth that whoever dies because of a stomach disease (al-mabtoon) 
          is a shaheed (martyr), and on the Day of Resurrection, when those 
          who lived an easy life see the reward given to those who suffered during 
          their lives, they will wish that their skin had been cut with scissors. 
           
Hence we hope that if your sister died 
          bearing her affliction with patience, believing in Allaah, doing whatever 
          she could of the obligatory duties, that she will have a great reward 
          and a high status with Allaah. We ask Allaah to have mercy on us and 
          on her, for He is the All-Hearing, Ever-Responsive. And Allaah knows 
          best.