the loss of one rat

Question
i used to have two rats, both girls and they are 4 years old. one had one huge tumour and one small tumour, and the other had  one medium sized tumour and was blind. last night, the one with the huge tumour died. i've left her in the cage for a day for her sister to grieve her. now her sister wont move or eat. when i pick her up, she just flops like a ragdoll. i knew that my rats would die soon, but i dont want the last one to die alone, but i dont want to leave the dead one in the cage because the alive one just holds onto her dead body. i dont know how to help my rat, because i dont want to take her sister from her! help!

Answer
Well 4 years is amazing for a rat considering the average lifespan is 2, so at least they had long lives.