Is this the norm for interviews?

You have the right to expect the same courtesy of the manager as she would expect of you.

If you were going to be late, you would have been expected to phone ahead and let her know. When you arrived for the interview, she (or a designee) should have let you know that she was running late, and offered you the opportunity to reschedule. While one or two brief interruptions may have been unavoidable during the interview, stopping 15-20 times to answer calls is over the top. If she is not well enough organized to conduct a basic employment interview, I would not hold out much hope for her overall management skills. That would lead me to question how she handles such responsibilities as scheduling, employee evaluations, disciplinary issues, ordering and stocking of supplies, etc.

There are many factors which should be taken into consideration when considering a job offer. The organization of the unit manager is just one of them, but one that would give me an unfavorable impression in this case.

It was rude for the manager to show up 45 minutes late without letting you know about it. Was she telling the people on the phone that she was busy at the moment, or did she carry on a conversation with them? She may not have any control over other people calling her, but she does have a control about how she handles the phone calls. I would not decline a position based on that, but I would talk to the staff and ask if they like their jobs. I did that before I got hired on, and my future nurse manager encouraged me talking to the nurses that I will be working with. That way you can get some real opinions and not base your decision on one incident.

What Jolie said - I've been on several interviews and the manager may have had to deal with 1-2 very brief things. Yes they are giving you a job but IMO many hospitals are VERY VERY competitive for new grads and they should give you an honest interview... what if you have a problem and you need to talk to your manager and she is THAT busy that you are interrupted every 3 seconds? There should be a competant charge nurse that can handle things while she interviews.