they could have beamed Yuta back to the Enterprise
By which time the murder of Chorgan would have already occurred. As it was Riker barely arrived in time, now add the small mount of time it would have taken for the transporter operator to scan for one person in the room (Yuta), lock on, and beam her out.
Chorgan is dead.
When Riker beamed in, Yuta was already walking towards Chorgan with his drink, where are these extra few seconds supposed to have come from?