> She used to live with another dog-a boxer. The previous owner said that used to leave them for most of the day when she went to work 9-5pm and she said that Truffle was fine to be left re toileting
It is possible that she wasn't entirely clean but that either she or the boxer removed the evidence - plenty of threads on poo eating recently!!
Do you feed her at the same times each day? On the days that you are home it may be worth making a note of input and output times - I have a dog of 5 who is regular as clockwork.
The other thing you might want to look at is the habit element of her toiletting. One of my dogs will often not go completely - he has half a poo, gets distracted, then finishes later; I've learnt to just wait him out! The other dog is much more likely to go if I'm not watching - he likes to takes himself into the long grass or under a hedge and he turns his back on me whilst going. With the exception of the late night outing, both boys are more likely to toilet after exercise - the walking seems to stimulate them to go.
I'm not sure a crate at this late stage will be the answer. At age 6 it's likely that your girl has developed clear habits and preferences - you may just need to understand them better and then factor them into your routines. Do check your partner is exercising at lunchtime rather than just letting her out. In the meantime when she is left on her own do confine her to an 'easy clean area' in case of accidents and, as others have said, go back to basics with rewarding her for going outside.