How to speak to a roommate who is miserable in the morning?

This morning was terrible. I woke up early because of a bad headache & sore neck. I was sitting on the couch having my coffee when my roommate got up. She walked into the livingroom & very miserably said "morning". I said "good morning" back without the abruptness that was given to me. I never went into the kitchen while she was getting her things together,nor did I get in her way. I sat on the couch. Just as she was going out the door., she said "goodbye" in a very abrupt tone. In reply I said.."have a good one" (cheerfully). I got a grunt in return. 

She has told me in the past that she doesn't like a lot of conversation first thing, but there wasn't any conversation. On weekends, she's just fine..she comes into the kitchen, says 'goodmorning'., & will carry a pleasant conversation.

I refuse to have to start walking on eggshells just because she's a b*tch in the mornings. How do I speak to her about this morning, or should I just let it go? If I had been the one in a rotten mood, she'd have addressed it the moment it happened. To tell the truth, her moodiness somewhat spoiled my day.