Is it normal to want to spend every second with your bitfriend?

My friend refuses to do anything if it means that she may be pulled away from her boyfriend. The only time she will make plans with someone is when he is at work. She won't even have a phone conversation if he is around. She will even tell you that she will have to get off immediately if he calls in the event that you reach her without hum around. I would gladly hang out with the two of them to spend time with her, but I'm never allowed this option. I just think this is a little weird. I guess it made sense when their relationship was new, but this has been going on for over a year and they live together. It seems to just get worse.