Should I say ‘doing’ or ‘being’?

Should I say ‘doing’ or ‘being’?

I can say that in our class we have our second mother, Mrs. Smith, our teacher. She cares for us, as if we were really her children. Sometimes she gets angry with us, but she has reasons for (doing, being) so. She worries when some of us seem to have problems. She even bonds with us, and we are grateful to her for doing so.