First and foremost I feel sorry for her on a human level. I've spoken a bit on here about how people speak about MPs can be very unsavoury. It's a difficult job and she will feel embarrassed and useless for a period. We should all hope she's okay.
Other than that, it does reveal a rift. Starmer and Reeves seem a partnership and seem a good fit irrespective of if you like what they are doing. I have to say this week feels like the beginning of the end. That may take years and may not be true, but it's rare for such a public display of unhappiness to be meaningless. Normally after such an event someone will think "things can't carry on like this", even if it's Rachel Reeves just thinking none of this is worth it for her own sake.