To add to the good advice from SAPMAN I'd like to mention that Marylou should just as easily be able to book as separate one ways the two segments of the outbound direct flight she was already eyeing. That would mean the fare savings and RR credit doubling are available with minimal additional effort. Bags of course should be checked through, but I think the only additional "trick" would be to be sure to do OLCI and bring printed boarding passes along from home. I haven't done this so I hope someone with real experience can chime in, but my guess is that Marylou could stay on board at HOU and give the home-printed boarding passes to a FA for scanning by the gate agent.