Property solicitor here - on a sale, there’s a form the seller will fill in (shown up thread) confirming who the other occupiers are. Babs should have been listed here. There’s also a pre-completion document confirming vacant possession on completion. We don’t physically inspect the properties - we will make the relevant enquiries of our client and relay their answers. In all honesty, if the client is an individual who lives in a property by themselves, and there’s no granny annexe etc, no one would consider it necessary to check the allotment wasn’t otherwise occupied (although I probably will now!!) but I’ll always double double check with them it’s vacant on completion.
As above, I don’t go and check, so if my client assures me it will, I relay that on. Frankly if I find out afterwards they’ve lied I’ll be pissed off! On what you’ve said, I don’t think either of the solicitors have done anything wrong - she’s just misled them, and you 🤷🏼♀️