Momoko's mom chose to close the manor instead of making her daughter sacrifice her much-loved carrier.
And I think we already have most of the picture of why Momoko hasn't been going to the manor, maybe she feels a little guilty that her best friend was "forced" to take over the manor in her place.
But I do have a feeling I may be overthinking this, and the reason is just... I don't know, she focused on her own life, Momoko is a very high-level geisha, she is busy and I think she just focused too much on it and kinda "forgot" to go back to the manor.
I know this one seems kinda ridiculous, but... it happens, sometimes life just keeps people apart, no matter how close they are/were, and there is no deeper meaning in it.