Sarah has not "waffled". Waffling entails saying one thing then changing your mind and saying something else. In other words flip flopping. Sarah has never said she would run and then backed out or vice versa. She will either announce at the end of this month or she won't. If she does, great, if she doesn't that is her choice, and only her's, to make.
Well, actually, she has said that she is still considering it. Some might say that she is still, therefore, making up her mind.
She has never said anything as definitive as you said: “either I will announce at the end of the month or I won’t.”
So, your version is very straight up. Saying, “I’m still thinking about it” is not as straight, some might say. In fact, some might even say if you haven’t actually made up your mind, that that could be called “waffling”.
It’s a subtle distinction, almost metaphysical. But bottom line, according to her own testimony, she hasn’t decided.
(Maybe she has, though, and this is all part of her grand strategy......)