If your girlfriend is manipulating you to get money by being distance and texting your older brother is it ok to pretend you still like her?

Is it ok to pretend you still like her and use her for sex until you have heard enough and then leave her ? I think it’s the only way to go when someone treats you like this ? Any advice ? I’m thinking to play along and just get the sex until I’m bored then make an excuse to break up with her 

2017-04-11T00:37:33.809Z