I think Dina's focus wasn't what was convenient for her ex's girlfriend but rather than what was in the best interest for MS's well-being. If you read Bove's report, he mentions an interview with RZ's sister who told LE that Max had demonstrated the scooter in the upstairs hallway. When the interviewer noted the scooter would have been on carpet, she said he rode it slowly, which does not fit with Gomez's theory that it was accidentally propelled over the railing. Dr. Bove seemed to have lotsa doubts about her story.
JMO
Dr. Gomez's theory doesn't involve a scooter at all. If you look at the drawing, it has Max running and then going over the portion of the railing where the railing dips. There is no scooter in that scenario.