It's like when a couple decide they can't live together anymore. Maybe the woman needs some space and wants to move in a new appartment. She doesn't have any issue with the man per see, it's just that she needs some space. These things happen. But then the man gets all grumpy and say "Well, ok, but then you'll have to make your own kids - you can't have shared custody of those we currently have. And you'll buy your own set of clothes, you can't bring yours home. If you want to quit me you must quit me at 100%, no exception! And the house? Find your own house!" Except that the man doesn't really want to have sole custody of his kids - it benefits him for his ex to have them every other weekends. And he doesn't really want to keep his ex clothes either - he has no use for them. Why not negociate with his ex for her to buy them back (assuming the men bought them first)? And he can't pay the house by himself anyway, so why not again make a deal with her? Brakeup don't HAVE to be messy.
I've always been suspicious of political argument by domestic analogy. This post is a good illustration of why.
Basically, because the analogy fails. But even within the analogy, the real problem that "she" will need to face is being glossed over. Who pays for the apartment? (which has one p in English, btw) Apartments aren't free, and "the couple" are already on a fairly tight budget.
It gets worse when you factor in the way that the analogy fails. Because in weltpolitik, there's no such thing as an apartment that you rent. It's all homeownership, and the houses are all not only rather expensive, but also badly in need of maintenance. So for her to get a place of her own and some space of her own, she's going to have to invest in some long-term financial committments, and develop quite a bit of skill at home repair that her husband has been doing for her in the house that they share. Quebec has never had to run her own currency, organize her own military, conduct her own diplomacy, and so forth; Ottawa has always done it for her.
Similarly, Quebec has never managed to bring in enough money to cover "her share" of the household expenses, which is why Ottawa has provided a relatively generous allowance of Federal money. (That's part of what I mean by "apartments aren't free.") An "independent" Quebec will either need to live within her own personal income (which is substantially less than what she's been getting in an allowance from Ottawa), or else find a new source of personal income outside of the relationship. Maybe moving into the new house will open up new business opportunities for her (she's closer to her clients?), but that's certainly not a given.
The other problem is that international law simply doesn't allow for "shared" assets or joint custody or whatever. Most countries, states, and provinces recognize "marital property" which is shared by two people; I own my house and my car jointly with my sweetie, and we share our mortgage debt equally. But countries can't do that. It's not "the man" that's telling her that they can't share custody of the kids; it's international law, which in turn fairly closely reflects reality. (Part of the reason is that in "shared custody" we can at least both appeal to a neutral court as an adjudicator if we disagree about the kids. But there's no international court to whom countries can appeal; they have to work it out between themselves by treaty).
Your analogy really does make Quebec independence sound like a bad deal. Either Quebec becomes a sovereign country in the traditional sense of the word, in which case she's assuming a load of responsibility for which she's woefully underprepared, or she is asking for a whole bunch of expensive freedoms that she wants the rest of Canada to pay for without recompense. "I want my own house, but I want you to fix the roof when it leaks and mow the lawn." "I want my own clothes, but I need to be able to come over and use your washer for free." "I want to see the kids on weekends, but I need you to drive them over and pick them up afterwards."