I don't know if they chose the order based on gender roles, age, or anything else. I think when you're naming a duet, it should be based on the flow of the names. In this case, I do think "Rodrigo y Gabriella" flows better than the reverse, so to me they are named appropriately. My wife's comment was just an off-the-cuff remark about who the better guitarist is, and on that I happen to agree with her. That takes nothing away from Rodrigo - he's a phenomenal lead guitarist, but when you watch them, you see that Gabriella is playing rhythm guitar as well as percussion, and doing an amazing job at both simultaneously.
For the record, I sign our cards with her name first, and she signs with my name first.