Do you think my friend is blowing me off? Making excuses, etc, etc?

I usually try to keep in touch with close friends. The other day I saw one of my friends and we got together for brunch, and it was 3 years since I've seen her! We usually talk on the phone and I usually give her a call every 2 or 3 months to keep the friendship going, so responds back and we talk, but usually if I don't call her, I don't hear from her. One time she changed her number and she didn't tell me, until I emailed her and told her that I was trying to call her. Also, I've invited her to my familys house for a get together and a baby shower, but she said that she was busy "working" or that she's got plans with her husband. She's married, has no kids, she works as a music therapist and is working on her masters degree. Is she really busy or is she blowing me off?