Declining the stimulus shown on TurboTax may delay your refund. The IRS has said it will calculate the correct amount of the Recovery Rebate Credit, correct your tax return and continue processing it. If a correction is needed, there may be a slight delay in processing your return and the IRS will send you a notice explaining any change made.
The stimulus payments were advanced payments for 2020 and based on 2018 and 2019 tax information. If you were a dependent, you would not have received a stimulus. However, because the stimulus is actually based on 2020 tax information, you would qualify if you were self-supporting in 2020 and not claimed as a dependent.
Keep the stimulus on your return. You are entitled to it.