Charlotte nodded, once the young man turned to look at her, as a way to confirm that such a discussion should not be addressed in a public place. It was rather strange, since she had just watched this man become hot-blooded, not too long ago, and he would miraculously show a calm and compassionate disposition. Obviously, he was truly a very caring person, who apparently has a flaw of acting on impulse. 
The blonde woman mentally kept that note to herself, as they departed the building, helping to escort Erina safely, before calling a cab. 
Once they were inside, she told them everything. From where she received the red-flag from Speedwagon, to where she was deliberately told to not come back to the scene, and seek them out. 

"Straizo was the name he told me, and that he would be looking for you, to finish the job that Dio started", she finished. 
"Whether Speedwagon survived, I don't know", it was a solemn and troubling thought, having to close her eyes, whilst keeping a compassionate hand on the elderly woman, who returned the action, in kind. 
"Dear child, I have known Robert for, as long as my husband did. Honorable and selfless as he is, he would be the first to ensure that you made it out alive first", it was a sympathetic remark, really to shed light that if he was indeed dead, then he made a noble departure to ensure Charlotte's safety.