Establishing boundaries and being consistent with them IS loving her. A huge part of raising children is training them to have control over themselves. We are all egocentric - literally 'self-centered'. I want what I want, when I want it, how I want it. A child does not outgrow that on her own. She has to be taught. If parents don't take the effort the train it out of the child, she will become a self-centered adult and bring much grief to herself and you and others.
So, do be willing to discipline her now. It's pay not or pay later. You don't need a lot of words. She understands 'no' by this time and action. Don't give her 3 chances - she'll learn she has 3. Just one chance and then the consequence. Do it calmly, cheerfully, but 100% consistently. She is a tough cookie.