If you file Married Filing Jointly, a new spouse's income is used to calculate your net income for purposes of calculating child support.
It is extremely rare for her income to actually be used for support of your children.
It is typically only an issue if you are not paying your support and Department of Child Support Services has to go after your money. Then if you have a joint account that she has deposited money in or that type of thing they could potentially get access to it. However, generally her income only matters in the equation for tax purposes regarding child support and is not counted as income. If you have other children and are trying to claim a hardship credit for those children, her income may also be counted in that.
This answer is a general interpretation of the law and is not fact specific to your case. Likewise it does not create an attorney-client relationship. You should seek an attorney for a review of your specific facts and documents. My firm is All for the Family Legal Clinic, Inc. a nonprofit public benefit corporation that charges on a sliding scale based on income and family size. For a consultation contact us 510-999-7732 or at our website www.allforthefamilylegalclinic.org