There are 2 things you can do anything about: carrying gear for her and minimizing the elevation effect.
If she is carrying 20 lbs more body than when she was in shape, she certainly will not do well adding the necessary water and extra clothing. Just remember, if someone else carries her gear, they must STAY with her. Frequent pauses for photography can help your patience
For elevation I recommend taking her to at least 5,000 for 2 days before. The anti-inflammatory benefits of Ibuprofen (vitamin I) help my body adjust to the sudden gain of 10K. Renew your first aid training so the warning signs to watch for are fresh in your mind. Every 1/2 hour "suggest" taking a break with her.
Above all, enjoy making precious memories together.