I love your enthusiasm but you need to work out where your priorities lie.
Firstly, what your parents think you should do with your life is no way to live your life. You will have to trust me on this- I know someone who was pushed through childhood by their parents to be high achiever and then basically coerced to go to vet school. They completed it ok but didn't find the course all that enjoyable. But the real grief began in the workplace- they positively hated every second of clinical practice and left not long after graduating. I cannot begin to explain the amount of mental anguish that resulted throughout of all this.
Second: engineering, medicine, dentistry- all hugely competitive, difficult and lengthy courses. It is no accident that they are long degrees and have pretty stiff entry exams and very high entry requirements. I wouldn't say any of these options is easier than the other. Maybe engineering will be shorter in duration but I wouldn't count on it- a lot of employers will expect a masters degree on top before they will even consider employing you.
Thirdly, I can completely understand your parents hoping you will pursue a worthwhile career that they percieve will allow you to earn a lot of money. However, in respect of medicine, unfortunately, this is no longer true unless you reach consultant level and/or become involved in private practice. Even if you opt to be a GP, with the shortest possible training route (10 years from beginning to 'end' give or take), the salary isn't that amazing in reality unless you are a partner (which means more work on top of your clinical practice). Dentistry has a similarly long training programme and again, if you want the big salary, top of the chain jobs, you're likely going to have to complete a masters on top and of course you need to have the manual dexterity and eyesight to be able to physically do the work- not everyone has this. Engineering perhaps offers more scope in the world of business and you can earn a reasonable salary but I'd like someone to correct me if I am wrong but I doubt any employer will be paying you 100K a year at the age of 23 barely months after you have graduated.
Of your list, I'd hazard a guess that you won't see many chartered engineers working nights, bank holidays or much outside of 9-5 Monday to Friday. Doctors certainly will be because which clinicians do you think take up the bulk of patient care on nights and weekends?
Dentists likely have a better work:life balance but again their training doesn't finish in year 5 of their program either.
My advice: if you're going to study something, then study something you are really really interested in and passionate about because it will be many years of grind to get there. Hard work is one thing, but hard work you do not enjoy is an entirely different proposition.
PS don't compare yourself to your sister, either. Live your life your own way.