In my experience all - ALL - Dominicans eventually ask for money at some point - one way or the other - male and female. Once a certain level of familiarity has been reached - they all do it. Unless, independently wealthy or from a rich family (less than 1%).
The simple assumption is this: Your flight and vacation cost what it take them 3-5 months to earn - assuming they even have a real job; therefore you are rich (subconcious and conscious)
In a sense. you are relatively speaking: you can spend that kind of money purely on pleasure and not the necessities of life.
They are compelled to ask - it's not a character flaw - it's instinct - imagine you dating a woman you knew to be a multi-millionairess - eventually you'd ask for something - if not money then maybe help with an investment or some such.
Furthermore, women in general (equate giving extended access to their bodies as something that will be compensated for either by way of commitment, money, security, status,......its always something and never truly free with them - unless the interaction is purely casual).
So the only question you need to ask is: what does she provide for you ?? and is that worth the money/time/energy/ investment - that she is asking ?? - is the interaction mutually beneficial after factoring in all your costs ?? if the answer is yes, then proceed. If and when is ceases to be, then leave.
Remember, the one thing Dominicans are not is romantic. So remove your thoughts from the realm of the romantic and to the realm of the practical. It is to be expected that if she has a gringo or man with means in her life, that he will be helping her - what she really actually spends it on is up to her. And don't think that giving money or not giving affects her fidelity - it doesn't (rationality being another trait that they don't have in abundance).