Her missing episodes from season 8 were spread too far apart to have anything to do with shooting the one episode for AMC -- it was likely just in her contract, either because of CBS or her own wishes. It's possible that CBS was trying to make some adjustments to save money at that time....several actors from NY had missing episodes as well & I remember one of the producers of that show said something to the effect that they wanted to change that because they knew it wasn't working. I haven't read anything about her taking time off either (at least not from the initial article that reported her returning, nor directly from Eva) - she said via twitter that she filmed 2 AMC episodes in one day & that the rest she would film in August. If she misses any of Miami because of AMC, it will likely only be one episode....if that. I believe that if tptb had any thoughts of having her head to the background in S10, they'd have axed her involvement in the cliffhanger. Horatio is a big draw to the show, he'd have been just as capable of ending the finale on his own & still left the audience on pins & needles. My opinion is that Natalia was there & involved for good reason.