So /she/ decides she wants an arbour in the garden. Somewhere to sit and
watch the sunset, but the neighbours can't see.

Find one, buy it, put it together. Mostly - then stop as I realise the
back panels are made of ply, and haven't been painted on the edges -
which might be a problem since the bottom edges sit in a cross member
that has a 1/4 inch wide groove in it, and will doubtless hold water.

Then realise the inside of the groove hasn't been painted either.

Ever try painting inside a 1/4 inch wide groove, deeper than it is wide,
without getting paint on the edges? I ended up using a model makers
paint brush

Andy