Ultimatums are bad, but we already know that. What is an ultimatum... It is when a person tries to force their will on another, it is about power. Think about when we demand a raise in our work, the boss does not WANT to give it else they already would have. But we tell that we will quit if we don't get it. If we are high value the boss will likely give in and give it to us. In that case, we used our power to demand and win and might have to do it again. Unions do it all the time.
We can listen to her wishes and then decide what is best and take much counsel from her. Do not let her insist and decide on anything that is directly against what you want. Don't be bull-headed and tell her no just because, really consider what she is asking for. In no way ever give in to her demand if you have made it clear to her that it is not what you want. Do try to see a way to accommodate her, but do not allow her to override your choice, ever. Once that is done once, probably can never recover.
It sounds like she is not grateful for what you have done for her.
Make sure you spend enough time with friends and family aside from her. You need some balance to what she is telling you. If all you hear is her, will be in trouble soon. Spend some time reading in this forum, guys ask similar questions all the time, it is really common.
If rejecting her ultimatums leads to a breakup, then leave or if it is your house, tell her to leave. Do not waver on this, you will regret it if you do and she will end up cheating on you before or after your married. 100% chance.