GOOD FOR YOU! I'm so excited that you are not resorting to any of the band-aid tricks, tactics, and money wasters that include supplements, shakes, meal replacement, food-elimination diets, detoxing, or other fad diets that slim nothing but your wallet!
Another vote for Weight Watchers - you sound like the type of person who needs to be educated in what it means to eat and cook properly and really understand why you're doing what you're doing. WW does just that and by educating yourself you will go much further than most as opposed to just reading a book and trying to do it on your own. Personally, I'm a clean eater BUT that's not something I would ever just dive right into if I were first starting out as it can be very restrictive and a huge change.
If you've been working out and limiting your calories, you might not be eating enough. At 191 pounds you should probably be eating at least 1600 calories a day. For any woman, 1200 is the lowest you should go. You need calories to fuel basic metabolic processes in the body and if you're not feeding your body then your body will hold on desperately to its fat stores, wondering when the heck you're going to feed it again!
You mention that your fat is in your arms, legs, and buttocks - I know this isn't what you want to hear but that is really good news! Abdominal and mid-section fat is also known as visceral fat and it's really bad and hard on the organs. It's the most dangerous type. Unfortunately though, you'll probably have the hardest time shedding the fat from the areas you mention. While it is true that you cannot spot train (i.e. doing a zillion leg lifts won't trim the fat off the legs exclusively), the body does some weird things at times when it comes to fat loss - we usually start to lose it in the breasts and face first. Legs (particularly inner thighs) and butt are typically the hardest.
Your personal trainer should have you lifting weights or strength training. If not, find another one. As a female you don't have the amount of testosterone necessary to become big like a body-builder man. What you will do, however, is add muscle mass and muscle requires more fuel while at rest in the form of calories - you'll turn your body into a calorie-burning furnace! The best part about strength training, in my opinion, is that it tightens and tones everything up. Shape and definition will give your arms, legs, and butt a much better appearance.
Best wishes and I am so proud of you for wanting to do it the right way! Don't give in to the quick-fix temptations; if they really worked would we be a nation with an obesity problem? Nope!