No experience whatsoever of this but just wanted to send some positive thoughts!
Don‘t chew yourself up about not having had her spayed, - the decision, whether it be for bitches or dogs, is always a matter of weighing up the pro‘s and con‘s and it seems to me that we‘re dammed if we do and dammed if we don‘t, we can only do what we feel is best for our dogs, which you clearly did!
We also have a very young foreign vet who has just taken over from our own who has retired so I understand your reservations but then I remind myself that he‘s been trained using the most up-to-date research and modern know how and he‘s also full of enthusiasm so although he might lack the practical experience, he‘s aware of the fact and is more likely to double check things.
Hope Willow‘s feeling better soon!!