Why didn’t my friend say “thank you” or responded when I congratulated her?

I asked her if she passed her classes and she said “Yes…”. I was like, “Oh goodie!! Congratulations! I’m so proud of you girl! That’s just great!” She didn’t say “thank you” and just straight up changed the subject.
Wow……that was very rude. I just brushed it off. I didn’t wanna irritate her. She could have at LEAST shown a little appreciation and say “thank you.”
Why don’t some people respond to “congrats” or “great job”? I was happy for her.
One of my former coworkers did the same thing to me at work when I congratulated him for his big promotion before I got fired.