What should a girl do whose father has passed away, and her mother is unable to work due to health conditions, and she and her sister cannot find work, and their father's pension and her meager wage do not cover their basic living expenses, and she fears resorting to the money deposited in the bank, which her father intended to invest its profits for dire necessity, fearing falling into usury, knowing that her father strongly refused to deal with usury?

If the bank where you will deposit your end-of-service bonus is a trustworthy Islamic bank that invests money in permissible ways and gives a share of the profits, then there is no harm in that. It is a legitimate alternative to dealing with usury (riba). So, search for the most reputable Islamic banks in your country and invest the money there. For whoever gives up something for the sake of Allah, Allah will compensate him with something better, as happened to Yusuf (peace be upon him) and the Muhajirin (emigrants).