My child changed her name and gender in July. Her social is the same as before, but she had a small income under her dead name, from before.

No. If the income is being reported under her correct Social Security number, the IRS can connect the income to the taxpayer.

However, not just for purposes of making the IRS matching easier, but for many other purposes, I would encourage your child to notify the Social Security Administration of her name change, if she has not already done so.