It is not the first time they have done it in close proximity (they had two Ninas one week apart earlier this year for example) but that's the first time I can remember that they did it back-to-back.
Not a huge deal though. If the girl wants to be called Mia and the other girl wants to be Mia...
Actually, no.
They just had two DIFFERENT Mias back to back.
The thicker one on 08/03 was Mia Costello as indicated above indeed but then they released a scene on 08/06 with a different Mia.
See here: https://mnvg.com/Thick_Body_And_Perfect_Big_Naturals_On_This_Latina
vs...