The fiancée visa requires the marriage to occur within 90 days, but the Adjustment can accur after the 90 days have passed.
Specifically, the relevant section of the law states:
214.2(k)(6)(ii) Nonimmigrant visa issued on or after November 10, 1986. Upon contracting a valid marriage to the petitioner within 90 days of his or her admission as a nonimmigrant pursuant to a valid K-1 visa issued on or after November 10, 1986, the K-1 beneficiary and his or her minor children may apply for adjustment of status to lawful permanent resident under section 245 of the Act. Upon approval of the application the director shall record their lawful admission for permanent residence in accordance with that section and subject to the conditions prescribed in section 216 of the Act.
Acceptance of WIC benefits is not generally considered recent of public benefits to the mother, but rather for the child's benefit. Therefore, this would not normally prevent a woman from receiving her Green Card. The details are important.
These are important issues and must be presented in an up-front manor, but in a way the does not invite delays and unnecessary inquiry into a range of issues. For this reason, an experienced attorney can be very helpful and help to achieve a rapid and uneventful approval of your green card.