It is a really good idea to keep her quarantined for at least 30 days, just to be safe. Many chronic respiratory diseases can lay dormant and flair up during times of stress, the quarantine period gives you the chance to see if that happens before you spread it to your flock. There are so many stories of people introducing sickness into a previously healthy flock, and it's heartbreaking sometimes. Caution will harm no one. She is very pretty, so hopefully all goes well and she's a healthy bird. If you think she is really stressed being alone, then I would choose one bird to put with her, let them get to know each other carefully, and then if she does turn out to be sick with something, you will only have risked one bird. Likewise, she will then have a buddy when you do integrate her into the larger flock. Some things to consider.
