If you don't want to risk breaking up with her, then you are in her power and she will continue to abuse you.
She is (presumably) an adult and responsible for her behaviour. This means you have every moral right to hold her accountable for the way she relates to you, and demand and end to her shitty and manipulative behaviour.
As a first step, you need to set clear boundaries that this behaviour is unacceptable and you will not tolerate. No need to be crude, but you need to be firm. Make your expectation that it not happen again absolutely clear. And then back it up. Do not tolerate abuse from her. She is an adult and therefore responsible for her behaviour.
In the short term, you can refuse to co-operate with her. Tell her right there and then to stop and that you won't tolerate it. If she continues, tell her to go get her furniture delivered by professionals. Just dump the cupboard in the stairwell, leave her at the dinner table or the party, or whatever the situation, and leave her with the problem of her own making. Do not cave in to emotional manipulation like crying and so on. She's the one who sucks for doing this to you.
Let her know that these tactics will not work on you.
If the behaviour continues, and you've discussed it, end the relationship.
Remember the golden rule: no one will respect you if you do not first respect yourself.