If a transgender person asks you to deadname and misgender them in front of certain people. Misgender them and deadname them in front of those people. It doesn't matter how icky or gross it may feel, it doesn't matter you'd rather be honest. It doesn't matter if there's more of you there. Certain people aren't safe, and honesty IS NOT the best policy when honesty could put them at serious risk. It doesn't matter if there's a crowd, because when there isn't shit goes down.

Be an ally, do what they ask. Understand that the trans person knows more about their situation than you do, and this includes who's safe and who's not. Some one can be "trans friendly" to other people, but not to people they know or specific people. Do as the trans person asks, yes it's uncomfortable, but it's 10 times worse if the person we don't trust finds out. 100 times worse if they have access to us when you're not around.

Respect trans peoples safety. Misgender and deadname when asked.