My only child, daughter will turn 17 tomorrow. She has the entire upstairs of the house. If a kitchen was up there, we'd probably never see her, LOL
She has been raised around a lot of people, lot of playdates... My house has always been full of children. They love to come here and I love having them because I know how I make sure they are not into anything bad. Now with this age, I still often have a house full of teens and I love it.
I've never been her "playmate" but we do a lot of things together such as cooking, we keep a puzzle on a game table upstairs and work on it as a family, she loves crafts, sewing and creating things so she has what she needs to do that as well. We communicate a LOT and do a lot together. She thrives on responsibility and her independence so I encourage that by giving her responsibilities.
I never expected her to stay in her room. As she has grown older, she does spend more time in her area (all upstairs) with her homework, projects, computer, gaming system, reading,boy friend, friends, etc. Actually, right now I find myself missing her a bit because she is doing more alone upstairs preparing for college, etc. She'll be off to college before I know it.
It is all a balance. Yes children need to be able to entertain themselves but they also need to interact with adults, especially parents and other children.
Your daughter is just 8... Engage with her, encourage playdates at your house. It won't be long and you'll wish she was spending more time with you and not in her "space" alone.