Is it considered a shortcoming or a sin for a female worker to buy some food for herself without buying the same quantity for her family, knowing that she buys for them according to her ability?

It is not obligatory for a person, when buying something for themselves, to buy a similar item for their family, whether they are children, parents, or siblings, rich or poor. Whoever finds a surplus beyond their needs must spend, in a reasonable manner, on those whose sustenance is obligatory upon them. If they do not find a surplus, then they are not obligated to provide for anyone else. The Prophet, peace and blessings be upon him, said: "Begin with yourself and give charity to it; if there is a surplus, then for your family; if there is a surplus from your family, then for your relatives; if there is a surplus from your relatives, then for such-and-such [others]." Therefore, there is no blame upon you for what you buy for yourself without buying for your family.