I don't know the answer to your situation, but if you've ever lost a parent, it can really mess things up. I know my reactions and emotions are usually outside the norm anyway...
You might not be able to help her actively, but I know when my husband was patient with me and waited for me to "come back" to him after my mom died and my dad got sick-it made all the difference in the world for me.
Good luck-it sounds like she's lucky to have you.
Heidi