Please help me determine this

J

I am 38 weeks and 6 days pregnant and up until today I was having a boy... today I told the tech I did not know the sex because it's the only way they would bother checking for me... well she looked around yelled and got excited and said it's a girl congratulations!

This is the picture she gave me.

Is this really a girl?

*** this bottom ultrasound was taken at 20 weeks at a ultrasound tech school by a student who's teacher confirmed a boy.

But I feel being 39 weeks it's pretty hard to make a mistake in determining the gender