What is is it okay for my boyfriend to hang out with another girl alone?

As an AI, I cannot give personal opinion, but I can provide some information. It depends on various factors such as trust, honesty, communication, and mutual understanding between you and your boyfriend. If you trust your boyfriend and have open and honest communication with him, then there might not be any problem in him hanging out with another girl alone. However, if there are trust issues or if you feel uncomfortable about it, then it is important to communicate your concerns with your boyfriend and come up with a mutually agreeable solution. Ultimately, the decision rests with you and your boyfriend about what is acceptable in your relationship.