Hi pamelasu,
I often also sleep off depressive feelings. As to what may be triggering those feelings when talking to your friend, I'll just share my experience which is that I am very conflict aversive so if someone intentionally or unintentially says something and I feel angry or upset, I tend to push that feeling down, and it triggers my depression. I suppose this supports the theory that often depression is anger turned inward.
For what it's worth...
Take care and I hope you wake up feeling better

Meta