Theo and Loki and Yelena
When the havoc kicked off, Yelena had to remind herself of Steve's directive not to use lethal means. He also didn't want the rebels getting too much exposure for their efforts, despite plotting an assassination attempt, because he knew they would be executed for treason. That felt like a tying of her hands, but Yelena would play ball and fall in line. It must be what the Avengers are used to with Natasha when she went legit and became one of the good guys.
Everyone else had their assignments with magical protection spells and decoys in disguise. Yelena would make sure their fellow bus riders all got out of the thick of things alright. She trusted Steve and Bucky to make sure those involved directly with the attempt on the king's life would get back to the bus. Roman was already halfway gone on whatever drugs he had taken for the evening, but if anyone could convince him to get it together, it would Peter.
A quick scan and mental headcount told her only Loki and the guy who mentioned keeping an eye out for magical ingredients were left unaccounted for. She went in search of them in each of the side rooms reserved for the gentlemen. She came up empty in the study, the billiard room, the gentlemen’s room, the gun room, and the snuggery. She still found the name funny. Snuggery.
Finally, as she pushed her way into the smoking room, she found the two men passionately entwined, pressed against the wall, with the Asgardian's thigh slotted firmly in between the younger man's legs. A few minutes later and who knew what she might have walked into?
"Really?" She asked by way of announcing her presence. "I mean, good for you both, but you have to do this now? We have an assassination to stop."