Hmm she's another nice looking type - bad pics again though! Reading between the lines she is probably being moved on because she's proved too much for the 13 year old. Which could mean anything or nothing of course, it depends on the 13 year old (!)... perhaps worth an enquiry and asking for some better pics and vids?
On a side note, it does slightly rile me when people market horses like her as having 'huge potential' ... she might have lovely paces and a scopy jump etc but she's 8 years old and has done almost nothing competition wise, and is clearly (at best) not 100% straightforward, so what is her potential really worth? If I was in the market for a horse to get to the grassroots finals or go BE100+ (which I'm not BTW, nowhere near brave enough!) I would either want a horse with a proven record at that level or something young, nicely bred and unspoiled (either of which would cost north of £5k!), or if I couldn't afford either, I'd be looking for a project horse to take a gamble on but £3.5-£4k is not a project price!
People do seem to think that 'potential', a pretty face and a few pics of the horse ballooning over a small fence or trotting around overbent can add a few ks to the price tag. Probably because they know they can't market the horse as a solid all rounder or schoolmaster which is where you can really make money out of average quality horses. For me I'd take a solid record at a low level, older or with some limitations/quirks over that kind of 'potential' any day!
But rant over (sorry!), she may well be a sweet mare in the right hands so worth a call about her.