I wish I could support my so's art on facebook better.
Why do you think you haven't supported your SO's art?
I've asked my sister about it and she told me she wouldn't feel offended if I didn't support her art at this moment
It is important to give your support your SO when they are doing something. It can really make them feel loved and appreciated.
I don't know if I'm ready for that kind of commitment.
If you're not ready for that type of commitment you might want to take a look at your relationship and figure out what you want from it. I'm sure your SO however wants someone who will support their art and if you can't be that person, you might want to let someone else be.