About to take the plunge, and I wanted to know if she allows filming, and if so, if it’s extra.

You will find very few if any pornstars that allow filming during the "session".

Pornstars are afraid that the film will leak to the net and since it's known that most pornstars escort they don't want evidence that they escort.

So don't cont on it that you can film it

Not sure about Jessa but some other stars will allow filming.  But they may or may not ask you to sign a 2257 form.  If there's no signed release form, then they could sue you if you posted the video online.  OTOH if there's a signed release form, they can always claim that it's a video shoot and not escorting.  But I'll leave that to the lawyers to decide if that would be a valid defense in court.  

Ask when booking, most have an up charge, The last lady I seen wanted an extra $500 for film and pics