To me her heart rate at the end tells me she was not stressed or tired. And if she eats and drinks just fine, then i'd say move up! I recently purchased a 5 year old gelding and his first ride will be in November and we are doing a 50 miler. As long as you know your horse is fit and the heart rates don't lie about fitness. Like Phantomhorse said we all are never "sure" about moving up. It took me a year before I did my mares first 1 day 100 mile ride because I kept telling myself she was not ready. Well she finished in 7th place with a ride time of 12 hours and was pulling my arms out at a 14 mph trot on the last loop and her heart rate and CRI was 48/48 at the ending vet check! I'd say she was more than ready for a 100! Haha! You will always question, but deep down you know if the horse is ready! Good luck!
Oh and by the way, great pictures!!!