Is anything incumbent upon the questioner, and what should she do if she circumambulated six rounds instead of seven, out of forgetfulness and not doubt, and did not realize this until after completing the Sa'y, shortening her hair, and returning?

It is not permissible to deputize someone to perform the circumambulation (tawaf) on your behalf. Performing tawaf with six circuits is invalid by consensus, as the pillar is seven circuits. If the tawaf is not valid, then the ritual running (sa'i) is also not valid. Therefore, you remain in your state of ihram, and you are obliged to return to Mecca to complete the remaining circuit. It is more prudent to repeat the tawaf from the beginning, then perform the sa'i. If returning to Mecca is impossible for you, then you are considered to be in the ruling of one who is prevented (muhsarah). If you had stipulated a condition at the time of ihram, you may then exit ihram, and there is nothing upon you. If you did not stipulate a condition, then you must slaughter a sheep with the intention of exiting ihram and distribute its meat to the poor, then you may exit ihram.