My mother almost died from a ruptured spleen and I did not pray for her.?

No, it makes you helpless in a situation that requires medical professionals.

I'm not sure you can be a bad atheist, a bad person yes, but since the only requirement of atheism is not to believe in something, I don't think it even matters if you pray, nothings going to come and get you for it anyway.

Whether you believe in the Lord or not, is truly up to you. But don't over think it. Such situations can barely be cured via medical attention and I can see where you might think that a prayer ain't going to change anything. The important thing is that she's alive, and if you're Religious, I would thank the Lord for giving you a future with her.

probably better you didn't

From a study on the efficacy of prayer:

"Prayers offered by strangers had no effect on the recovery of people who were undergoing heart surgery, a large and long-awaited study has found.

And patients who knew they were being prayed for had a higher rate of post-operative complications like abnormal heart rhythms, perhaps because of the expectations the prayers created, the researchers suggested."

Atheism has no requirements. If you want other people to tell you right from wrong you should get religion.

You would be a bad atheist if you prayed.

That choice does not necessarily make you a bad person, in and of itself.

Yes, real atheists pray to science.

Do you really think that prayer would have extended her life?