Thank you for your question. In general, children can have rapid changes in their behavior or mood but it usually doesn't last very long if its attributed to age-appropriate development. If the changes persist and are more generally rather than specific to situations or people it could be for a variety of reasons. Ideally, it would be nice if you could get a clear answer from her about what is happening to make her act out but she probably does not fully understand herself and she cannot verbalize it.
Nevertheless, you can work on discouraging negative behavior as you described in what you've "already tried" section and there are some other techniques to supplement what you are already doing. If you take games or toys away, do not keep them away too long or it will lose its effectiveness.
Positive reinforcement can be very effective in changing behavior. For example, "I'm taking your toy away because you were rough with your friend. If you can play nicely and gently for the next 3 minutes you can get it back" It important that young children have the opportunity to earn privileges back.
Providing a natural consequence when children misbehave is also effective. When she is actively participating in negative behavior, intervene immediately. Give a time out (one minute per age) offer choices and the opportunity to change behavior. For example, " You have two choices. "You let everyone take their turn at playing and you are nice or you do not play (or we go home)". Then keep your word regardless of her reaction.
The key is consistency and fighting the temptation to lose your temper or give up on the techniques because they do not seem to be working. Its a natural tendency for children to test their parents stamina with keeping the rules and boundaries. They can test for a long time but will stop when they learn that you cannot be overturned.
Therapy is also an option if you feel the behavior is worsening and is interfering with her functioning. Find someone who is comfortable with young children and has experience with play therapy. Ask her if there is anything that she is worried about, is making her nervous, or she is confused about. Ask if she is having bad dreams, did she see something on TV or the news that scared her, is she worried about a family member. You get the picture, there can be so many reasons with young children. If she denies, as children often will when they are scared or embarrassed, tell her to talk to you if she thinks of anything or remembers that is bothering her.
I hope you find this information helpful.