No, the girl who left the line was not the one using a scooter. The scooter belonged to someone in her party. Also, the girl who left the line was 14 - 15 years old although, it’s possible she looked much older. When she went and told her family about the party pushing her around when she tried to rejoin the line, that is why her older brother was so upset. This was a kid.
Edited to add, there’s a ton of reasons that a person may require a scooter that has nothing to do with walking. That’s quite insensitive to say. Looking at my mother, she appears to be a fine, fit, woman however, she is actively dying. While she can walk to and from the lines just fine, her heart and lungs cannot take walking around Disney all day. So, a scooter it is.