My Sister Has Been Constipated For A While, She's Gone

My sister has been constipated for a while, she's gone to the doctor and they only give her laxatives. She's been in these laxatives for about 2 months now and she still can't poop right. I did some research and bought an enema for her. I'm a little nervous because she thinks she might have hemorrhoids. My question is: is it safe for me to do it to her? Can anything go wrong here?