If you're not willing to tell her "no," either at will or even at your own detriment, you'll lose her respect or never even gain it.
That being said, if the only time you say "no," is out of spite, you'll come off as a petty/whiny bitch as well which is just about as much of a buzz kill.
Learn to just refuse to do something she asks, and if pressed for a reason, don't provide one.
"I don't feel like it," is an acceptable response is said with an even tone/keel.
I can't reiterate this enough.
Learn to say no and stick to your guns.
Period.
You'll have to relearn this lesson over and over.
Saying no inevitably subtly helps you operate not from a place of scarcity but 1) knowing she will accept your refusal and that 2) on a larger scale is she balks then walks....you will stick to your line in the sand and not give chase.
The ironic thing about this?
They will virtually never leave when you do this IF done correctly.
When you learn to not sweat women leaving you, the bizarre thing is they virtually never will.
It's a lesson learned in blood and one that totally changes your paradigm of interaction.
Eventually, when I slept with enough women, a lot of the(ir) magic was lost on me.
This equated to numbing me to their flailings and desperate cries for whatever....you sleep with enough and you see the numbers in the matrix. You see her tacit resistance, her emotional hangovers, her emotional push/pull, her pushing your buttons out of playfulness or genuine mean spiritedness......
You see that the harder her resistance pre-sex, the more she melts in your hand after the first dick in the vagina incident.
You see that the harder a time she gives you verbally, the more she's projecting.
A secure person doesn't need to tease others maliciously.
A secure person isn't afraid to say things that the other may not like or find offensive.