Well the fact that she started walking and counting calories is a huge step, she just needs to stick with it and she needs to make sure that after she gets to her goal she continues to do cardio and have a good diet. You can support her by working out with her and giving her encouraging words. I think setting small goals for herself would make working out more fun and she will slowly see progress which will make her more confident and more determined to stick to her MAIN goal. If she starts making excuses then all you can do is push her to keep going or maybe change the routine so she doesnt get to sick of it. When she does hit her plateau she will need to change something that she is doing(increase the cardio or lower calorie intake).
Hope i could help you