Originally, I agreed with the consensus that you should just go. It's just one day.
But the more I thought about it, the more I realised I couldn't come up with a good reason why you should go.
This women was effectively a stranger (you haven't spoken in nearly 2 decades) and the fact that she liked you is not a good enough reason to attend her funeral. You haven't indicated that you were really good friends in the past, and if you were I doubt you would be here asking if you should go.
I hate to pull the uno reverse card or to speak ill of the dead but let's be honest, if the roles were reveresed nobody would be telling you to attend the funeral and some choice words about them being an incel would crop up.
If you decide to go to be nice, that's okay. If you decide not to go because it is too wierd, that is also okay. I don't think there is a wrong answer here.