"Oh… that's true…"
"..."
Everything went just like the doll 'predicted' from the encounter with Rouge to Lupa's proposition. However, Alexandra was growing more suspicious by the seconds. She just realized something, a reasoning error that the doll pushed her to make.
Let's say that this doll could truly see the future or at least possible futures. That didn't prove her goodwill at all. In fact, she could be working together with her rumored master so that Alexandra would end up dead. It would be unusual to mention her master's intentions then, but if that was their plan, she had to admit it was clever. You wouldn't suspect someone trying to save you, at least usually.
Of course, there was still the possibility that the doll was sincere. But even then, she couldn't be sure she could trust it.