Sejal is Riddhima's only friend and it was not shown Kabir killed her or not, so I will think positive that she is still alive.I think Sejal is dead .
There were traces of her being alive .
Sejal called when vansh Cliff incident and riddhima doesn't lift the phone seeing her name .
Riddhima saved Kabir's number as Sejal in her phone .
It was not Sejal calling .
Which means there are no evidences that Sejal is alive .
She is definitely dead , uski wajah se Kabir ne vr mansion main itni adventure kiya hai aur riansh se insult alag aur job bhi gayi .
Woh nahi chodega Sejal ko after all that siyapaa , she created in vr mansion .
So , most probably she is dead .
If the makers want her to alive she can be back , because they never showed us Sejal dead (loop hole ).