Try sending your savefile before the beach, in the saves I have you help her sister (she gives you a footjob) you see maria working out in the living room at the evening, johanna asks you out,you see maria working out in the living room by night, you find maria with her friend speaking about an aphrodisiac and she uses it on you, you assault her in your room and later she gives you a handjob in her room, next scene with maria is the beach scene. Try reading Maria's computer every day in the morning not to lose any entries
Here is my savegame of the beach day, you can compare the variables if you cant find what is missing
