Being an unmarried girl, while watching any inappropriate sexual photo/ video , I have a discharge, I dont know what it is; urine or vaginal discharge. Is ghusl e janabat wajib after it? Sometimes there is no discharge, but feeling of urine starts; again I dont know whether it is sex need feeling/urge or simply the need to urinate. Would ghusl be compulsory in this case?

First of all avoid such forbidden acts, these things brings difficulties and hardship in this life for believers, and sever embarrassing position in front of our beloved Allah swt, He swt give us all the pleasures yet we disobey Him and not be embarrassed from Him while He is watching us.

Any vaginal discharge that is associated with the orgasm in the female is a cause for the obligation of the Ghusl, however, there are other types of vaginal sticky fluid are discharged without orgasm on sexual excitement, but do not obligate the Ghusl,

Whenever there is no orgasm then the doubtful vaginal sticky fluid is considered pure and does not require any obligated action, unless if it was certainly urine.