We have a a family of three daughters (7, 5, 3). We are very family orientated and spend our days together. Daughters are good friends and play together no issues. Our eldest, though wants to spend time alone with her friends when she has playmates over. I do not know if it is that I do not want her to grow up and being to strict but I think the whole locking herself in her room should happen at an older age. I probably know what you will all say but I need to hear that I am wrong and should let her spend her time alone with her friends and not be bothered by her little sisters...Am I wrong for thinking she should still share her space with her sisters regardless if her friends are over?
You aren't wrong, or right. If your family philosophy includes her sharing space with her sisters then you should encourage that and talk about why you think it is important. If she is at a developmental stage where she wants to spend time with her friends, then try to find a way to respect that.
She wants to spend time with her friends, and it sounds like she wants to spend time with her sisters - just not at the same time. She might also want a break from her sisters and the only way she can think to get it is by having friends over. Your oldest's friends probably came over to play with your oldest, not your oldest and her sisters.