Is the speaker sinful for letting the birds die due to the cold, and what is the expiation for that if it exists?

The questioner erred by leaving the sparrows in an air-conditioned place, which led to their death. The Messenger of Allah (peace and blessings be upon him) said: "Whoever kills a sparrow for no reason other than its rightful purpose, Allah the Almighty will question him about it on the Day of Resurrection," and "If what you do to animals were forgiven for you, much would be forgiven for you." However, whoever repents and seeks forgiveness, Allah will forgive him. Allah the Almighty says: "And whoever does evil or wrongs himself then seeks forgiveness of Allah will find Allah Forgiving and Merciful," and "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" We advise her to follow up a bad deed with a good deed that erases it, as Allah the Almighty said: "Indeed, good deeds do away with evil deeds," and His (peace and blessings be upon him) saying: "Follow up a bad deed with a good deed, it will erase it," and "If you do wrong, do good." And she should beware of despairing of Allah's mercy.