Will she go back to WDW with you one day? I mean is a trip planned?
I can understand that she is a little scared off now, maybe she is also a little ashamed and does not want to happen this again.
Maybe you could motivate her with some goal to reach until the next trip. Something like "lose XX pounds until the 201X trip". A few pounds can already make a difference in this case.
I think when someone does not fit into a ride it is time for a change, most of Disney's rides are somewhat generously built to fit in many different body shapes. In her position I would not ask myself "do I fit in other rides?", I would rather think "what can I do to fit in ALL rides?"
I went with some friends some time ago to a local theme park and one of my mates had to exit a free fall tower ride because the shoulders retraint's position was not what it was supposed to be due to his size. He lost more than a lot of weight since then and he never encoutered the same problem again and is somewhat happy for that incident because this changed his perspective on his weight and his body.
So: motivate her!
I hope nobody is offended by this post!
It's a lovely idea, but weight loss motivation comes from inside. She has to want it and be ready.
Her body also has to cooperate.
My husband has been working to lose weight since 2012 (and before, but more half heartedly), I know what he eats and he should not be the size he is.
He has been shamed countless times though his life both from the outside (his mother who put him on a diet at 3 and her horrible words have never stopped, strangers at
Disneyland, etc) and the inside (he wants to ride the big rides at universal!!! and riding Goodys Sky School at DCA might be fun too). None of it had worked. He has a pituitary tumor that he's been treating since 2009 and it makes it so hard. Doctors had ignored him for years, just telling him to diet, to exercise, etc, while all the while this tumor was growing.
This next endocrinologist visit he's going to ask for another in depth panel to be done and see if there's something else hiding.
He's willing but it's not working.
The OP hadn't mentioned her friend's weight in this thread so most of us I think figured pulling out the lap belt would help. Alas her size is such that even the belt trick might not work.
I have seen what it does to a person emotionally to not be able to fit, and I feel so much empathy for her.