When you are filing jointly, there is no "her" refund. You are combining incomes and taking all deductions, exemptions, and credits you are allowed as a married couple. The TurboTax refund estimate only takes into account the information that has been entered up to that point. So if you entered your filing status and then your wife's income, it would estimate your return using that income and all allowable deductions (some of which are yours). It would then drop the refund based on your winnings.
The only way to truly separate your tax situation from your wife's is to file married filing separately. This typically results in a larger overall tax obligation than if you filed jointly.
