Pregnant mare with swollen vulva

[Nagling]

Hi We have a 3 month pregnant mare and I have just noticed she is swollen between her anus and her vulva. Everything is a normal looking colour and there is no discharge at all. She is not bothered about it. Its soft swelling not hard. Any ideas?!! Many thanks in advance

 

[cruiseline]

Could she have been stung by a bee or bitten by an insect?

If it does not go down over the next 24 hours, I would get a vet to check it out.