I'd want to know if it was her first foal (and if not, how long ago was she previously bred from, was she a good mum, any complications etc) and more recent pics- assuming the ones in the ad aren't from last week, as there's no conformation shots.
So yes, I'd be wary- how have her circumstances changed so much from she was going to have time for in-foal mare-mum & foal to having no time for just one (tho possibly a personal question!) but otherwise she looks/sounds nice
I agree with the others but it could be that she had a change of circumstances, thought, "I know I'll put the mare in foal so I don't need to worry about riding for a year" and has realised that this doesn't actually help her much.
I bought a registered 11 y.o mare a couple of months ago (happened to be the right colour and the right breeding) she had a filly at foot, turns out to be in foal again (I'm not so pleased about that, but there you go) and I now find out that she is known on the circuit and was rather a good penning horse sold to an amateur that lost interest. Fit, sound, sane, owner just wanted rid, sold to a dealer, he made a quick $200 profit out of me. I'm not compaining, if I'd been suspicious and hadn't made a few calls I would have walked on by and missed out on a really good horse.