I'm confused about the wheelchair thing - is she expecting them to automatically provide a wheelchair for her due to age, or is she requesting one explicitly?
Sometimes they get put on the wrong passenger, sometimes the passenger decides not to use it.
No airline staff is going to assume they are carrying an infant as they are not allowed to travel alone. But they would definitely assume as wheelchair request is an error or mistake.
As per the article, airport staff did expect to carry a baby.