We did microbiologyc testing before her season and everything was well. We made three times progesterone testing with vaginoscopy and our vet told us we need to mate my girl after one and two days when her progesterone was 5/ng (at the 11th day of season). So the matings are done in the 12th and 13th day of her season. I checked my girl every day after mating, and on the 5th-7th day I saw a little whitish discharge from her vulva. It was really just a few, with no smelling. I think if I not checked her every day, maybe I not see it... It could be normal or a good/bad sign? It is stopped on the 7th day. She is happy and eat well, not licking herself. Now we are on the 12th day after mating, and it is the 24th day since she started her season.
Im pretty scared what was this, can anyone help with some advice? (Sorry for my english, im from other country.) Thanks!

Despite being mated, she will have remained 'in season' up to the usual 21+ days.   All you can do at the moment is keep an eye on her and any discharge you see beyond the time she'd normally be out of season, should be checked.   It is possible she could have picked up an infection.

I have found that every bitch I have had mated which is 12 over the years has a clear/opaque discharge after her season and mating.... Sometimes it has been yellow.... I would not worry so long as it does not smell and does not turn back to red/brown/black. Sounds very normal,at the moment.

Thank you very much both of you!
She is still happy, and this little discharge is totally disappeared. I only saw it on the 5th and 7th day after mating, but I will examine her further.