Is a Fidya (expiatory sacrifice) obligatory for someone who performed Umrah but did not shorten their hair, then performed another Umrah and shortened their hair in the hotel, knowing that the hair shortening was only from the upper part?

Shortening the hair (taqseer) is a ritual for women, and without it, one cannot exit the state of ihram (definition). Since you did not exit ihram from the first 'Umrah (definition), you are still in a state of ihram, and your second 'Umrah is invalid. You must refrain from the prohibitions of ihram, then shorten your hair. There is nothing upon you for what has passed due to your ignorance. Shortening is not necessarily done at Safa and Marwa; it is permissible to do it in the hotel. What is obligatory is to shorten the length of a fingertip from all of the hair.