I fear that not everyone has good sisters. I know a sister (not mine) that is conniving, spiteful, petty, shallow, and snobbish. She is awful.
The nicer one (see my post in platonic erotic massage) was wonderful, nothing like her sister. She loved her sister, but couldn't spend any time with her. "I love you like a sister" to her would mean that you want to take something from her.

Families can suck, too.