I'm so sorry to hear about your loss!
I know what you mean as far as grades, before the accident I had a 3.8. Immediately after I think I had a 2.1 and since then, each semester, it has gone up a little until now I have a 3.1. I think it has been a combination of me healing and learning to cope with my injury. I also find that school is a very good distraction, I can't give into my weakness or I will fail out. I can't sleep in, I can't skip class, I can't not study or I will have to leave. My question always is if that would be so bad, but I realize that I wouldn't have any idea what to do. I got my concussion second semester of Freshman year and now it is second semester of Junior year. In the year following my first concussion I got at least 6 more and saw 8 docs who couldn't tell me much about what was wrong with me, but now I understand a lot more.
Stay active, keep studying, get someone or a couple people who are understanding and don't mind helping you with your homework and who enjoy doing the things you can do. This is what helped me. One of my good friends even read some of my homework aloud to me a few times when my headaches and light sensitivity was so bad that I could not read myself. The first few months are the hardest, but after that you learn how to live.

It is hard, but you will become a stronger person from it.
Again, I am so sorry for your loss!
Good Luck!
Margarite