How long between litters after C Section?

This is not for me, one of my friends that has a Clumber Spaniel, the bitch had a litter just over 11 months ago, which ended in a c-section, she has now come into season and she intends breeding from her again (last time as she is now 6 and her seasons are every 12 months) My Daisy and Poppy had a section last time and I don't think I would breed from them for at least 18 months between litters as it seems a bit too soon.

What time do you think should be left between litters after a c-section?

i would say 18 months even in a bitch that has 1 season every 12 months i think they should have 1 season in-between litters, how many litters has she had? its a hard thing when something like this happens and they are getting on a little