Don't be so quick to judge. The delay in taking a picture is in the
main due to the focus system - if you press the shutter half way to
prefocus then when you press further to take the picture it is
essentially instant. The focus system can take different times to work
under different lighting conditions - for instance taking a view on a
sunny day will usually be very quick, but try taking a picture in low
light, or especially a contra jour shot (sun behind subject) on a
bright day and it will take longer.

When I went to digital compact originally I missed this point, so when
I upgraded I took particular notice of it. From my own research and
tests I have found that the quickest seem to be Casio and Canon, with
Fuji and Sony (W range) not far behind. Much the slowest are Nikon and
Olympus.

Also don't get caught in the race for pixels. To print a full frame
picture to A4 only requires 3Mp, anything above about 6Mp will start
to run into thermal noise problems, so for general use and to allow a
little cropping 5-6Mp is about the optimum.

I have three digitals: an Olympus C5050 (5Mp) which is horribly slow
but has probably the best lens, flash, and metering system by far
(compared with a compact) bar a little barrel distortion at the widest
setting; a Nikon D70s SLR (6Mp) which I love; a Canon Ixus 60 (6Mp).
We have just come back from holiday in France where between us my wife
and I took nearly 1200 shots (the beauty of digital!) - I didn't take
the Olympus. Generally speaking it is almost impossible to
differentiate between snapshots taken with the Canon and the Nikon (in
jpg mode.) I say snapshots as the one thing you can do with any dSLR
but NOT with a compact is to catch a moving object successfully. No
matter how fast a compact responds it will never match the near
instant reaction of a dSLR.

As a photographer for over 40 years man and boy I would give the same
advice as I did when people used to ask me which (film) camera to buy.
You have got to live with the thing: no matter how many bells and
whistles it has if you cannot hold and use it comfortably it will
rapidly fall into disuse, or it will be blamed for poor pictures when
a poor picture is solely the responsibility of the idiot taking it! (I
have fairly large hands and so could never get on with the Olympus OM1
film SLR as it was too small, but the Minolta XG2 or XD9 was no
problem being about the same size but just a few mill thicker to get
may hands around.) Take your SIL to a good camera supplier - Jessops
or Jacobs nationally - on a quiet day and have them get out the
cameras that are in her price range or thereabouts. She should hold
them, play with them, and take some pictures. (If the shop doesn't
have a charged battery - as Currys and PCW probably won't just walk
away. If they can't be bothered to provide that facility do they
warrant your business?) As sure as eggs is eggs one camera will feel
right - that is the one to buy. If more than one feels right then look
at facilities against price and ask if most/any of those facilities
will ever be needed.