No she's not right. When it comes to what you do with your time, you should always have the final say. And you should never let her conquer your time.
Take your gym clothes and use their facilities. Play it by ear as to how often and for how long you work out when you're on holiday. If there's nothing better to do, go to the gym. If there's something better to do, do that instead of going to the gym.
There should be a high proportion of the time when you have something better to do than going to the gym, because you'll be on holiday with someone you love.
Check what you've been eating and drinking for your niggling injuries, as well as you checking the nature of the exercises you've been doing.
Aim for anti-inflammatory foods and drinks, instead of pro-inflammatory. Aim for foods that enhance strength and stamina, eg fenugreek and beetroot. Aim for foods and drinks that promote cardio vascular health. Back ache, for example can be a sign of early cardio vascular disease, due to the blood vessels around the spine getting clogged and providing less blood to that area than previously.