Are you my sister?

Because she expects me to cover her all the time, because I am married and have 2 incomes and she can't hold a relationship together and is single.

Example:
Sister: Let's get mom present X for christmas and split the cost.
Me: OK
Sister: I think you should pay 2/3 and I should pay 1/3.

She has been coming to my house for the last few years for her "vacation" and expecting me to pay for everything because she is a guest in my house.

I don't invite her any more.