Going back in time a little bit, after Ren was done with his love confession and his first kiss with Sasha, Mirtha happily returned with a large grin on her face. Just looking at her face, anyone would he able to see that she was in a very very good mood.
From this, it was very easy to understand that Mirtha was keeping an eye on them. Sasha had already expected that Mirtha was definitely not going to leave them alone here even with the protection of the barrier, so this was not unexpected to her at all.
Actually Sasha was glad that Mirtha was this understanding. Without her being a silent supporter, they probably would not have been able to have this confession.
And even though it was not something that Ren had expected, he was not dissatisfied with it. The only emotion that he currently felt was a little bit of embarrassment. And he also understood why Mirtha had left them alone and he was very grateful about that.
