How long is a piece of string?
Hysterectomy is major pelvic surgery and as such carries an increased risk of DVTs.
Most people reckon that after 6 weeks you should be OK and back to 'normal'
Most patients actually manage to do better than that and are able to do most daily activities well before that. Especially if they had a vaginal hysterectomy or laparoscopic hysterectomy.
Flying to/from Spain is around the 3 hour mark and as such would normally not be associated with the risks of DVTs which have attracted more attention (but ?proven) over the last 24 months or so.
So as per usual there is the information and you can now make up your own mind. As you say probably good idea to the ask the medicine men/ladies involved in the care of your missus when the time arises.
HTH
FD