I wouldn't go as far to say ultimatums come from a powerless position. While anyone can issue an ultimatum, you should not realistically expect it to work unless you are coming from a position of power.
For example, your boss saying "You will not make anymore personal calls on the company phone, or you are fired"
I would say that your boss comes from a much more powerful position than you do in that situation, and chances are you are going to listen to him.
Oh by the way, that refers to ultimatums outside of relationships.
In relationships, ultimatums should ALMOST NEVER be given. The fact is people don't like ultimatums, and you are effectively putting that person in a child's place when you give them one. You know how you hate it when someone treats you like a kid? Yeah. Other people don't like that either.
Especially when it comes to the topic of sex. I promise you that if you tell this woman "have sex with me, or were through", you are not getting sex. An ultimatum like that would only work on a woman with low self esteem, and I'm guessing this woman considers her body her temple.
There is a place for ultimatums in relationships, but only if the relationship is worth saving such as in a situation where you have children, and other than the problem are still very much in to eachother. (Say you give your spouse an ultimatum to stop drinking if he/she has a drinking problem, or see a counselor if he/she has an anger problem) But in the context of single life, and especially if the ultimatum is over sex, and even more if the problem with the sex is that there is none an ultimatum is not appropriate in this situation.
My answer: No ultimatum. See other women, and wait it out to see what happens, or next her.
