Kate's answer is on how to make sure that you understand your girlfriend correctly, which is not bad, but I feel doesn't really answer the question. As someone who experiences something similar to what your girlfriend might experience, I would like to share how you can support her.
Reading what you have described about your girlfriend, I feel I can relate to some extent. In the sense that when relating to other people (as friends or more), oftentimes there is this guilt that I have not done enough, or that I do not conform to the ideal friend that I would like to be. This usually leads me to either reluctant to say no (if the other person is asking something), or for me to quick to jump to promises (which I feel is ideal but I didn't consider my capability in doing that).
Fortunately, recently I realized that there is this disconnect between my ideals and my capability. And that I disregarded that people can like me as I am, not as I would like to be. This is I think the major step in being able to be released from that "obligation to promise to do nice things". Once I realized that in relating to other people, other people actually want to know me as I am, to know what I like and do not like to do, I felt more free. In essence, the issue is about self-worth. I think this is quite common in Asia.
To check this, maybe you can ponder on these questions:
- Can she be assertive on she wants? Or does she always put her wants behind your wants? Being assertive is a positive sign of accepting self-worth.
- Does she do this to other friends too? Or only to you? Perhaps she has too high standard on what a girlfriend should do. You can clarify with her about what you expect and mention a few things that she did that you appreciate as bonus but definitely not in what you expect/demand from her.
- How often do you two do things that she enjoy? Does she feel bad after doing things that she enjoys together with you?
She needs to accept that you love her even if she doesn't promise to do stuffs (I say this since you mention "I don't mind not spending time together. Both of us have our own lives and I respect that."). So, you can encourage your girlfriend that you accept her as she is, and that you are interested in what she is genuinely interested too (if that's the case).
The "I don't mind not spending time together. Both of us have our own lives and I respect that." is something good to start the talk with her. Have you told her this? Then you can go further by assuring her that you accept her even if she doesn't offer to meet (this is a slightly stronger statement than the previous one).
It took me a year or two, though, to realize that in relationship people see more than just what we do, but also who we are. So expect changes to take some time.