To answer the first part of your question, I don't believe it is frowned upon to get a master's degree from the school you receive your bachelor's degree from.
As far going back to school right away or working as a nurse first, I have some insight. First, depending on the master's program you are applying to, they sometimes want you to have related experience as an RN before you go on to a master's degree/advanced practice nursing. Nurse anesthesia school is one program that normally requires you have 1-2 years or experience in the ICU (intensive care unit) before applying. Also, some facilities will pay for at least part of your tuition in advance practice school.
As an RN hoping to go back to graduate school to get a master's degree soon, I can say from personal experience that working on the floor before you further your education can be very valuable. Nursing school for a bachelor's degree prepares you for many things. However, working consistently in one area really improves your skills at working in the healthcare environment in a way that school can't really prepare you for. Additionally, working on the floor gives you a better perspective on healthcare in general.
With regards to this better perspective, I started out in nursing wanting to become an ICU nurse and going to nurse anesthesia school. Through experience on a cardiac surgery step down floor, I found that definitely wasn't the right path for me, and switched to working on a cancer floor. Now I am preparing to get an advanced degree in something that I didn't even know existed when I was in nursing school!
Nursing is fantastic because there are so many different areas that you can practice in, and no matter where you are you will impact peoples' lives. I think what is important when you are in school and starting out is being open minded to the opportunities that are out there, having a drive to learn, and a drive to help people. Of course, if you have something that you are set on doing and feel ready to go to school for it, go for it!