Can Omega-3 really help with weight loss?

My sister is 23 years old. She is taking amitriptyline 10 mg HS. She has migraines with aura (she sees a neurologist). She goes to the gym at least 3 times a week and is followed by a kinesiologist (workouts of at least 1 hour). Her diet is not perfect, she eats chips and everything, but she is making a big effort lately in this regard. She is trying to lose weight. She saw an article about losing weight by ingesting omega 3. She is a vegetarian and therefore would like to have plant sources. I would like to know if taking omega 3 is really beneficial for weight loss and also what dose is required considering that plant sources of omega are less well absorbed. Thank you for your help!