Hooooow do you discipline your sensitivitie child😫

Kit

My daughter's 3 and all attitude and I'm strugglin hard. I feel like she's well mannered (I've been a stay at home mom almost her whole life so I've always been with her, trying to teach and discipline her appropriately) she's well behaved in comparison to other children I see and listens to her grandparents or Dad when he has his stern dad- voice. So I feel like she KNOWS to be well behaved....

But when it's just the 2 of us, she's a different person!😢 It feels like she doesn't listen or acknowledge I'm speaking to her at all unless I scream, which makes me feels terrible when I snap like that:( But also, more often than not, she's incredibly sensitive, has always been this way, if she's told no in any way, she just screams and squalls and I feel horrible, but insist on standing my ground so as to not reward that. But some days it's just exhausting, and feels like a fight all day that I just don't have the energy for. And I also don't wanna stifle her feelings. It's ok for her to sensitive, and I don't want her to mess her up emotionally:( Leaving the house is out of the question. I cannot handle the meltdowns alone when we try to get out and run errands:( She's not spoiled and undisciplined....I've tried so hard to remain consistent in our ways so that she knows what's acceptable and isn't but I'm really just having trouble balancing her sensitivity with trying to be stern in raising her properly:(