I want my sister to visit.
Why do you want her to visit you?
My family has to stick together and we must be there for the occasions like this.
You are a good family member for wanting to be close with your sister during important times. Family should stick together no matter what and if you abandon them it can cause unnecessary stress and distrust.
But I want my sister to visit right now.
It's good that you're close to your sister. Given the current situation, her visit now us unlikely, though.