That's not the way I took it. Sui got her old ring the very moment Takako suggested that she wanted to cancel the wedding, before she stated that she, 'understood why they couldn't be in charge of the inn.' The rest of Takako's lines are supporting her belief that Sui hates her. Takako has the impression that Sui thinks she is reckless (from all her stupid schemes). Takako was more likely trying to prove herself (for Enishi, for herself, for society, doesn't really matter). Her schemes and Enishi being a bit of a dummy are why she said the line about Sui thinks they're not worthy to run the inn.
Arguments supporting Takako's belief that Sui hates her, arguments that she isn't worthy of being Sui's daughter in law. Sui's story really meant that she and her husband also faced tough times, but it was good enough that they wanted to stand by each other. Where Takako was mistaken was in thinking that being given the ring also meant that she and Enishi should take over the inn. Sui gave her the ring because Takako admitted she wasn't worthy...which in turn makes her worthy. Humility is a big thing for Sui, even if it is the antithesis of her own daughter's disposition.
As for Momiji, wasn't there a line a few episodes ago about how he was away visiting family? I'd be far more willing to believe that he was telling Sui that he was going to retire, and that his family had offered him a place in their home, wherever that is. That's why her expression was both accepting yet wistful. He's been with them the whole time, and thus his departure would make her sad. It wasn't something she said to him, it was something he said to her. "This is my final work log," or something to that effect.
edit: It wasn't the finances book. Sui and Enishi handle that. It was a work log. Unless the boilers are going to explode, it isn't something that will close down the inn.
That outcome supports my belief that Sui will ask Takako and Enishi to support the other successor, be it either Ohana or Satsuki.