$2000 is the limit for the "Nanny Tax' to kick in. So, you do not need to pay any taxes or file any paper work.
ALL income is reportable. So, she is required to report the income on her income tax return. Since it is under the $2000 limit, she is not subject to FICA (social security and medicare tax). Whether she actually has to file a return, would depend on how much other income she has.. $1800 of earned income is under the filing threshold.
This assumes she baby sat in your home. not hers.