Is this betta male or female?

[Kotaraine]

I got this betta about a month ago, she was sold to me as female but now I see a bit of a bubble nest starting so I’m wondering if it could be a male after all? I’ve tried using a mirror to get her to flare up but shes doesnt seem to react. I only had one betta before (had him for almost 5 years before he passed!) so I don’t know a whole lot about them other than how to keep them. I attached a photo of her and also her bubble nest for reference

 

[Essjay]

I think it's a male. The pelvic fins (those hanging down under the head) look a bit long for a female.

You could try holding a mirror up to the tank. If the betta flares look at the gills. With a male, the gills will stick out at the side and under the head making it look like a beard. A female will only have gills showing at the sides, there won't be any under the 'chin'.