I'm a believer that most people can do it without surgery. That's not to say that some don't need it. I think you need to seriously try and change your lifestyle before you consider surgery. Forget fad diets. They rarely work and a lot of people gain once they go back to old eating habits. I keep trying to work on a generic help list, but off the top of my head.
1. Your old style of eating has to go. The method of losing weight should be a way of eating that you enjoy. It's not good enough to lose weight and then go back to eating what you eat now. Obviously you're going to just gain it back.
2. Find something that works for you that you could do forever. Learn to cook if you don't know how. Do not rely on frozen dinners, 100 cal snack packs, etc. Ask yourself can you really eat this way for the next 40/50/60 years? If the answer is no, find something you could do.
3. Pick a reasonable starting calorie level. I'd suggest at least 2000 calories (you can adjust it down later if after a few weeks it's not working). You're not going to get the 10 pounds in 8 days that fad diets will give you, but who cares.
4. Track every bite of food you take. Get a kitchen scale and weigh things particularly high in calories (peanut butter, cheese, nuts). And a Tb is level, not rounded.

You may not have to do this forever, but it should give you an idea of how much you're taking in now. Myself, I know I'll need to track until I'm at goal, and probably for a while after.
5. Avoid too many empty calories, especially in liquid form. This means coffee drinks filled with sugar and cream, soft drinks, and fruit juices. They don't give you a lot of bulk for your calories.
6. Find an activity you enjoy doing. Swim, bike, hike, lift weights, whatever. If you enjoy it there's a better chance you'll continue it. Start slow. You mentioned your sister - even better, find something you both want to learn. I was always horrible at tennis, but that might be fun (free if there's a park with a court).
Myself, I like to cook, and enjoy taking recipes and making them lighter. Egg whites mixed with a single egg makes just as nice an omelet as the 3 or 4 egg ones I used to make. An ounce of cheese in my omelet is just as nice as the big handfuls (guessing 2 oz) were. I still eat a wide variety of foods, and I'd class little of what I make as diet food. I've served meals I make myself to company and nobody knows the difference.
I discovered that I love lifting weights. I'm lukewarm about cardio (walking, jogging, treadmill), so I do less of it. I may (as I get lighter) enjoy the cardio more, but the lifting I know I will keep doing forever.
Wow, kind of preachy at times, but I hope you find something of use in the post. Best of luck.