Yes, she messed up because she allowed Roger to make it all the way through her territory and steal a cope of her Poneglyph. How do you see it feasible that the Roger Pirates sailed into her territory, made it past all her Islands and guards, made it to Whole Cake Island itself, waltzed into her castle, made it to the room where the Poneglyph was locked away, stole a copy, and waltzed right out without some kind of resistance put up from Big Mom's side?
1. These pirates are familiar with each other and even if they're "enemies" we know that they don't actually fight each other seriously.
2. The poneglyph is now locked away because of Roger's actions. Reading into her words with base logic spells out why she keeps it under tight lock now. Before Roger, none of the other pirates knew what to do with these stones. Roger was the person who made them significant and something important.
The entire panel and even the Oden flashback makes it rather explicit they didn't fight. Let's read with context shall we?
1. Big Mom tells Brook that he can't have her stealing her Box and in the same very sentence, includes her Poneglyph in that conversation. In the very next line, she says she can't have someone making off with their Poneglyph and going to to Raftel and said that her allowing that to happen would be stupid and laughs.
2. The way she speaks about this whole ordeal is one in which she was "outwitted or outright tricked" rather than it was forcibly taken from her. If she fought, her words would make it far more clear because she would be speaking far more aggressively. She is a woman who is egotistical about her individual strength to the point where she insults people for thinking they're able to do anything against her. The Ace Novel makes it clear that she has been unmoved and undefeated for decades and was someone other Great Pirates were weary to mess with.
3. Why would she include Brook alongside Roger? Brook is an ant to her. The only reason she would include Brook with Roger is because their methodology is the same (trickery and underhanded theft). And to reiterate she literally laughs about it would be stupid of her to have it stolen from her. If he beat her and took it, she wouldn't be laughing. She would be holding a grudge that sentiment is only displayed when someone pulls one over you.
4. Word travels fast in the one Piece world. Do you seriously think that if they fought her, that the world wouldn't know about it? Do you really think that they could fight and have it end so quickly? In the Oden Flashback, Roger says, that they stole the poneglyph from her and the rest of his crew responds "Thats Great Captain". If you're going for a fight against another Great Pirate like a real pirate, you bring your whole crew not just a few people. If they fought at all, in any capacity, we would know about it just like we know about Roger and WB fighting and its hyped to high heaven despite them engaging in a play fight where they took breaks.
Don't twist panels because any manner of reading comprehension and logic makes it crystal clear no fight took place.