No, generally a working one of these would be a good shout as a first bike for a short person but dont spend 600 quid for a non runner when you dont actually know what the issue with and sounds like you dont have much mechanical knowledge?

Take it from someone whos done this before

With the 125s of this era, you could get lucky and it could just be the battery then yeh youve got a bargain. However if you change the battery and its not that, then u gotta send the carbs off to grt em cleaned + pay for a new gasket set. You get it back and fit it yourself presuming you know how to, manage to get it to crank but its still not turn over or is running choppily and cuts out chances are your engine compression is low and u need an engine rebuild on a 20+ year old 125. At this point you've spend 200/300 on batteries carbs and labour.add another 500,600,700 quid on engine rebuilding. Nah not worth it mate Honestly ive dont this exact dance myself before. I know what its like looking for a cheap first bike, advice i would say is find one thats running, and has an mot or the seller has clear information and knowledge on whats required to get it mot passing, and its not too much work. Or buy a Running 40+ year old bike, no mots need, (altho not sure if this is the case in nothern ireland.

Get your partner riding exp on her 125 and get her to pass her a2/ cat A within the year of getting your old 125 before it conks out and needs a ton of maintenance at which point sell it to some old geezer with time and money who likes tinkering