Just get her spayed, she dosnt need the experience of having pups, neither do you, how would you handle if her pups are dead at birth, or have difficulties/deformities? what if you lost her during labour? what if she rejected the pups are you prepared to feed those pups every two hours night and day, can you afford a c section if she cannot give birth? can cost £1,000 depending if its out of hours or not, are you prepared to take back any pups that new owners decide they dont want anymore for various reasons? are you prepared for them to go into a rescue when rescues are already overcrowded? As you say she was never bought to breed from, your vet has given you advice re spaying to prevent cancer and yet you are prepared to ignor that to breed from her? a bitch should be over 2 years of age before breeding and should have all the relevant health test for that particular breed this in itself is expensive, its not just a quick once over at the vets its having proper test done, have a good think about it and realise the possibilities of having to sit there in the middle of the night with your pregant girl dead in your lap because you wanted her to experience having a litter.

Mo