Having a Sibling Move In

My sister has been begging me for months to let her move in. I have thought long and hard about this and this wasn't the easiest decision. You would think it would be easy since she is family, but there were so many things to think about.

1. How would this affect our relationship? Could something bad happen from this?
2. How would my mother react, would she feel abandoned?
3. The privacy issue.
4. Would she be dirty? Loud? Crazy? Annoying? I haven't lived with my sister in over 10 years.
5. What if it didn't work out?

We were also thinking no because we have really enjoyed our privacy of not living with other people. Yes we have lived together for 5 years with only around 6 months of having a roommate, but going back to old ways will be hard. But this is something that I can get over, not a huge deal.

But we decided to say yes because of everything that she's gone through. My sister and my boyfriend get along well, and I get along with her better than I used to, so I'm not worried about that. It was actually the boyfriend's idea to have her move in ASAP because of all of the problems that have been happening lately where she lives now.

Anyways, I plan on charging her around $200 a month for rent. I can't decide if I want to do that or charge her around $100 plus 1/3 of the bills (gas, heat, cable, etc), so that she can get a better feel of how expenses are and how her use can fluctuate by month. What do you all think? I'm leaning just towards the fixed number so that it can just be easier every month. 

Honestly, I just want to give her a nice place to live that will bring her life back to normal and that's why I said she could move in. She hasn't had a home cooked meal in forever (except when she comes over to my house), and I would like to fill that void that she has. I guess I will be trying to be more like a motherly figure. I want to help her with basic things in life that she should know about.

I do hope that us living together will help our relationship. Yes I know this is a far stretch because usually roommate situations do not go well, especially with friends and family. However, I haven't lived with my sister since I was about 12 – so she was only 8 (I moved out at 12 and moved in with my dad), so we don't have a really strong relationship there.In the end, I'm extremely happy about her moving in.

I'm sure most girls dream about having that GREAT relationship with their sister, and this is most likely my chance at that. We've never been close, but now we just might be. I would love to call my sister my best friend.

Have any of you ever let your sibling move in? How did it go? 
Do you have any tips for us?