Hey!
Good for you for wanting to learn to eat in a healthy way, because a lot of maintaining a good weight has to do with eating properly.
Because of your history, you'll probably need to plan out your meals and snacks, so that you always know when and what you'll be eating. This can keep you from feeling afraid to eat, or from eating too much.
One good balance of food groups is the Zone percentages, namely 30% protein, 40% carbohydrate, and 30% fat. Those are percentages of calories. Some of the computer trackers, like FitDay, show you percentages as well as calories. A vegetarian sometimes has trouble eating enough protein without sending carbohydrates too high, but it can be done. If you can change to eat fish and/or chicken, that can help with the protein.
The general guideline is to make sure your average calories don't go below 1200 per day. That's because it's very hard to get enough nutrients below that level. (Some medically supervised programs go below that, but the clients have to check in every week with the clinic to make sure they're OK.)
Do you exercise regularly? That's often a good way to make sure you lose less muscle, which can be a problem. Muscle is what burns fat, so you want to keep your muscles healthy.
If you exercise 3 times a week, then you could start right around 1600 calories per day and see how that goes. You may feel that that's a lot of food! But it may work. If after 2 weeks you are not losing, you can drop to 1500 calories per day. These are averages, of course. And see how that goes.
Healthy weight loss is not really rapid. A rate of 1 to 2 pounds per week is healthy. Any more than that for an extended period could mean that you're losing too much muscle and other tissue along with fat.
Good luck!
Jay