Sadly Spytty, the answer to this
does it really take away common sense thoughts and deeds from the sufferer?
is yes, that is exactly what it can do
what your mum used to rationally think through, she is now most likely just immediately (unthinkingly) responding to - she wants to take in the washing, so she goes to do just that - the link to her mobility problems and the fact (obvious to us) that these mean she will have difficulty with a task she once took for granted just isn't being made (the part of her brain that used to make such links is no longer working as it was) - she isn't aware that she has mobility problems (it doesn't matter who has told her or how often) so to her there are no problems, she is fine and can go get in the washing as she always has
YOU know she has to use the walking frame - she KNOWS she can walk just fine
she may have used the frame when the mobility team were there - but that was then; she's not retaining that information as the part of her brain that used to do that is not working as it used to
I guess your mum has always been able to come out with a quick quip, which is what she did with the neighbour - it's a good cover up strategy
a hospital stay is often followed by worsened confusion, which may improve, however it may not
I'd let the care team know about this particular concern - there are door alarms linked to carephone systems which can be installed
maybe looking at this thread may give you some more ideas as to how to respond to your mum
http://forum.alzheimers.org.uk/showthread.php?30801-Compassionate-Communication-with-the-Memory-Impaired
best wishes