I'm going against the grain here and I'll be her cheerleader without the negative comments that seem to have followed in others posts...
I think it's great that she is choosing to invest in her health. I think it's great she's chose to get a PT that will guide her through her fat loss journey. PT's and gyms can be expensive and I don't know how much that one charges but so what? It is an investment. She could have easily just went to the gym and not have a clue what she was doing etc. but she chose a PT to LEARN. What is so wrong about that? So that she can get it right. She will learn about nutrition and fitness. She also will burn a lot more calories than your average sized person due to her weight so she will likely still be on a pretty high calorie diet (which will still be in a deficit) so she can still have things like a bloody festive toastie. Why can't you all just say well done to her for making a better choice. Is it long overdue? Yes but she's made it now. It's also incredibly hard as a bigger person, to walk into a gym full of fit people so maybe get off her back a bit and stop the "well done" followed by a negative comment.
I don't support a lot of her choices and she has been very unhealthy for a long time but I will support ANYONE willing to put the work in to better their health. Doesn't matter how long it took her, what matters is that she has started.