I say definitely dump her. She seems like an insensitive and selfish friend. It sounds like the only reason you want to stay friends with her is because you have so much history, but you can't keep an unhealthy friendship going just out of habit. It's a bad habit. People change as they grow and just because you and this woman got along 16 years ago doesn't mean you're still compatible friends now. You both already have the idea of ending the friendship in mind so do it now while you can.

And I want to add that I know what you're going through. I'm in a very similar situation. A family member of mine died unexpectedly 2 years ago and I saw my "best" friend (also of 16 years) the day after the funeral. Not only did she not ask me how I was doing or express any condolences to me, but she actually complained to me about how she had a bad day at work because one of her co-workers annoyed her and expected me to help her get through her bad mood. Since then my whole perception of her has changed and I realized our entire friendship I always helped her through everything, even the little problems of daily life she should have been dealing with on her own, and she never so much as asked me how I was doing. Now I really don't think I want to continue the friendship, but she just got engaged (to I guy I don't really like and who I think is awful for her no less) and I'm sure she expects me to be a bridesmaid, if not her maid of honor. And since I'm sure she sees no problem with the friendship and wouldn't see it coming this is pretty much the worst time to end the friendship so I think I'm stuck until after the wedding. So I repeat - if you want to end the friendship get out now while you can.