What do I say if I’m asked to speak at my sisters funeral this Saturday?

I think that, given how you saw her and felt about her, that it might be best if you took a pass on speaking at her funeral. You can say you prefer not to do it, no explanation needed.

"i knew my sister when she was alive, i preferred her that way"

Since you've constantly insulted your sister in the past ("with cause', according to you), then the best thing for you to do is to decline to speak.  If you wanted to show her respect, you should have done that while she was alive, and made peace with her while she had a chance to hear it from you. 

Remember a happy time a better time I'm sure there were some.

Google what to say. Say nothing negative. 

We all know the reason you can't post an obituary is because there isn't one.

LOL in your sample all of those examples prove everyone's point -- they're days out of date. None of them were posted the same day as the death.

Pics or GTFO  .

How about, sorry, YA, for not being a very good troll. I was dull, repetitive, and lacked realistic detail in every single one of my posts.

Say, wow, how did we manage to get a funeral date so quickly in the middle of covid? The funeral directors must have been working overtime given my pretend sister only died hours ago.