nannies

I am a nanny for a family of three children, I've just cut down to 30 hours a week after recently getting married and wanting to spend more time with my family rather than my work family. Anyway, I am supposed to finish at 6, I think I could count the times they've actually been home by 6 on one hand! It's now ten to 6 and I get a text saying she is still waiting for her transport so will be at least another half hour maybe more. I'm tired, it's been a long day, I don't get overtime no matter when they come in, I'm always early for work every single day, I've never once been late. And right now I'm just pissed that my life has no respect from them, my husband is at home, dinner is in the oven and will be cold by the time I actually get there and I'm just sick of it! So question, if an employee is contually early for their shift, is it really unreasonable that they also get the same respect and finish when they are supposed to?????