that's true, but schengen visa is another list of requirements so then try to get multi entry visa to UK then another for Spain if even possible due to such weak passport
Considering it's two different visa you need for her and unsure if Thai's take holiday inside a holiday. But I would ask Thai embassy in UK if she can travel to schengen country while on tourist visa to UK
you go to immigration apply extension, then leave the country, by car or plane, come back in on another 60 days that can be extended again for 30 days. If timed correctly you can be almost 9 months on it..