I don't want to marry my gf purely for financial reasons
Why do you think your girlfriend wants to marry you for financial reasons?
I have a high paying job and I know she's attracted to me because of my money.
If you know that your girlfriend is marrying you because of your money then it's good to end your relationship. A marriage based on money and not love won't be very satisfying for you.
She is smart though. Does that mean I should never marry somebody poor?
As long as your relationship is based on true love and you are both devoted to each other, the financial status of your girlfriend should not matter. You can build a financial future together that will be strong because of the love you have for each other.