They alluded to it in the extra bit at the end - that we would have to 'wait until series 3 to find out', I really hope they do!!
It is pretty accurate - for those who want to know and no future spoilers - there was a poison scandal and athenais was suggested, incorrectly, to be involved following her connections to a real-life 'fortune teller' who was in reality a raging alcoholic.
don't read this bit if you don't want any info on the true historical bits which come after
Athenais did fall out of favour with the king, but not until much later in life by which time they had many children rather than the one I have only ever seen referred to on the dramatisation (who died). Several died but several survived and he was good to them all and gave them titles, despite being born out of wedlock. Athenais was always held in high regard by the whole court until she was much older when she 'retired' elsewhere in her late middle age. The king always dealt kindly to her and kept her well. The only animosity shown was around the poison scandal, but that was dismissed quickly. Madame Maintenon and Louis did end up married but again, much much later on both in their 50's/60's and well after Athenais time. We know all this because of lisleottes prolific diary keeping and letter writing. By all accounts she was a real character and athenais and Marie Terese did indeed 'select' her together, and they were praised for such a good match for Phillipe. Want to know anything else? I've studied this period a lot! Happy to answer!
safe to read now
If you follow george blagden or Alex vlahos on twitter they often post behind the scenes pics or updates. And the dialogue between the actors is very, very funny.