My wife Helen and I had a 2400 dollar stimulus check intercepted because I owe back child support to the state of CT. I need to get her portion of the check back

See this IRS website for information - https://www.irs.gov/newsroom/why-the-economic-impact-payment-amount-could-be-different-than-anticipated

Past-due child support was deducted from the payment

The Economic Impact Payment is offset only by past-due child support. The Bureau of the Fiscal Service will send the taxpayer a notice if an offset occurs.

For taxpayers who are married filing jointly and filed an injured spouse claim with their 2019 tax return (or 2018 tax return if they haven't filed the 2019 tax return), half of the total payment will be sent to each spouse. Only the payment of the spouse who owes past-due child support should be offset.

The IRS is aware that a portion of the payment sent to a spouse who filed an injured spouse claim with his or her 2019 tax return (or 2018 tax return if no 2019 tax return has been filed) may have been offset by the injured spouse's past-due child support. The IRS is working with the Bureau of Fiscal Service and the U.S. Department of Health and Human Services, Office of Child Support Enforcement, to resolve this issue as quickly as possible. If you filed an injured spouse claim with your return and are impacted by this issue, you do not need to take any action. The injured spouse will receive their unpaid half of the total payment when the issue is resolved. We apologize for the inconvenience this may have caused.

See this TurboTax support FAQ for filing a Form 8379, Injured Spouse Allocation - https://ttlc.intuit.com/community/accessing/help/how-do-i-file-form-8379-injured-spouse-allocation/01/26228