Here's what you do: You and your colleague sit down and document every instance of absenteeism that you can recall over the past six months. Write it all up in an E-mail. Check your spelling and grammar.
Then, hit delete and don't worry about it any more.
There is absolutely nothing you can say about an absent coworker that won't come across as whining and lacking in team spirit. It's also not your problem. The problem you have is a management problem. Your workload increases when your coworker is out, so address the workload.
It's perfectly acceptable to go to your boss on a day that your frequently absent coworker is gone—a day you are expected to do her work—and say: "I need a little help prioritizing. I was scheduled to do x, y, and z today, but now I also need to do a, b, and c. I'm not sure I'll be able to accomplish all of it, but I'll try my hardest. What would you like me to focus on?"
Note that your coworker's name never came up. It shouldn't.
Your manager knows she's out. HR knows she's out. The company president now knows because you told him. (Telling him, by the way, is over the line. Don't do that again.) They are either dealing with it or burying their heads in the sand. Either way, you bringing it up again won't make them change their approach. They'll just start to resent you.
There may be something going on behind the scenes that you aren't aware of. Your coworker may have an illness that qualifies her for many days off, through FMLA. Your boss and HR would have no reason to share that information with you. In fact, I think it would be unethical for them to do so.
Work with your boss on your workload, but let everything else go. It's not your problem. It's the company's. Let it be.
Suzanne Lucas has nine years of Human Resources experience, most of which has been in a Fortune 500-company setting. She holds a Professional in Human Resources Certificate from the Society for Human Resource Management. She blogs at Evil HR Lady