It's really wonderful to hear how much you have done and are currently doing to help your daughter. She is blessed to have such a loving and caring family.
I didn't understand 100% but I think you are asking about how to set up the playroom. Well I would set up a space in the house (her bedroom or a spare bedroom would be ideal) where you can lock the door and work with her one to one. Please view the "Autism Solutions" ideas on our website for more help of what to do in the playroom. See the link below:http://www.autismtreatmentcenter.org/co ... utions.php
For what to put in the playroom, you want to have plenty of soft things for her to throw, a couple of large yoga balls, maybe a small trampoline (depending how old and big she is) and things you can play with that she likes (e.g. pens and paper, books, dress up clothes, puppets/dolls, musical instruments). But nothing electronic or with batteries.
There are so many benefits to having a playroom, the main ones are that in that playroom your daughter will get much more control than if she's outside of the playroom. You will allow her to play with what she wants and if she's doesn't want to play with something, you will absolutely honor her "No". If she wants to ism (stim) then you will join her and wait until she shows some interest in you before you interact with her. This will show her that people are useful, attractive, easy to be with and she can trust them. They are predictable to her. It will be easier and more fun for her to connect with you and interact with you when you are going with her instead of against her in some way.
Around the house, or outside of the house, you may have to be setting lots of boundaries and saying "No" to her much more, so she doesn't get that experience that people are great and fun to be with! Also, her world will seem "out of control" to her so when she gets control in the playroom, she can relax, unwind and focus in on people more easily. The second benefit to the playroom is that she does not have any distractions (e.g. the window to throw things out of, or sensory overload coming in at her from all angles), again making it much easier for her to focus and attend to things for longer.
About her drinking too many fluids. This is a case of you setting boundary on how much she drinks. You are her parent so as her caregiver, so you can say how much she can drink. I would limit her fluids and explain to her that she only gets so much per day and then when it's all gone, it's all gone.
I terms of her peeing, limiting what she drinks will help. Keeping her in the playroom and getting a camping toilet will be a way to more easily facilitate her when she looks like she is ready to go. She could also be looking for a reaction from you when she does this (perhaps you feel uncomfortable when this happens). Maybe you could lay down some tarpaulin to protect the floor for now while you help her to use the toilet consistently.
I hope this has been helpful.