All these characters has someone for them to not commit suicide
And i guess that person for Sara was Sana.
But after last update, does she think Sana is too far gone?
I don't think so, but she will still do something drastic.
I highly doubt it.
1) Sara had blackouts at Sana's age
2) Sara knows Akira has blackouts
3) Sara knows that Sana was starting to see things, which would be a precursor to blackouts
4) She has acknowledged that she knew she was fighting with Sana for Akira's affection, and that Sana sleeping with her teacher was in her blood.
Putting all that together, she knew that an Akira/Sana hookup was an inevitability, and the only question is whether it would be one of them losing control and forcing the issue due to blackout or it being consensual -- and the video intro makes it clear that Sana consented (but it's not clear to Sara that Akira ISN'T blacked out).
It's an event she knew was going to happen, but hoped it wouldn't. She'll be heartbroken, but not suicidal.