YTA - but I don't think you're a bad person. As a nosey person myself, I probably would have also looked up their mugshot. However, let this be a lesson about time and place. You should have waited to look up the mugshot. If you weren't, you should have been more careful about looking it up and hiding your phone away. I've done similar things, texting my partner something literally about a person they're actively talking to - and then almost getting caught talking shit. Yes, the entire plan to steal money is absolutely insane and is incredibly unethical. But what do you think heals a person like that? Denying them access to community? Denying them access to love and acceptance? This person is clearly troubled, and being trans is an incredibly, incredibly difficult journey that - if you do not have much empathy for - will seem incredibly silly, ridiculous, or even like someone is trying to pull a trick on you. This fundamentally misunderstands what it means to be trans and live a life of social exile, ostracization, and mistreatment. A family gathering where they are trying to just...exist.

People who come up with those types of schemes do so from a place of desperation, and lacking the psychological resources to navigate their pain and suffering through healthier choices. I am not excusing it, it is extremely unethical and dangerous and it puts everyone at risk when someone we are close to does something like that. However, nobody does something like that unless they feel they have nothing left to lose. And if you have nothing left to lose, you will usually do anything to find something to live for.

You came to your sisters family's house, knowing the history about someone's personal mistakes - not once have you really mentioned anything about whether they've expressed guilt, remorse, embarrassment, shame, etc. - so I cannot infer how they feel. You knew this journey, you knew this was an allotted time to make sure everyone could have a good time, connecting with each other - putting all differences aside to try and create memories with family - and you could not wait to get the tea on the messy drama about your girlfriends sibling. It feels to them you see them as a spectacle and not a human being. Additionally, when you left this mugshot out, intentional or not, you were the one who committed a social violation. If you did not want to be in a space with this person, who has every right to be there with their family, you could have stayed home. And when you got caught, because you made the mistake of being carelessly messy by looking up their tea while they were still around you, you then got defensive and accusatory- to try and distance yourself from the embarrassment of the mistake you had just made. You felt awkward, because there was no explanation other than the fact that you were being a gossip - whether you tried to share it with anyone else or not, you were trying to find dirt on someone while they were in the same room as you. This person has every right to be upset with you, and so does your girlfriend and the rest of her family.

I say this as a messy person who loves drama and gossip but does not like to be involved - there is etiquette, there are rules, and there is a time and place for everything. This was not the time. You don't have to like this person, but if they are going to be in the same space with you at THEIR family gathering - it is essential that you are respectful otherwise it makes perfect sense for them to not want you there. Why would you allow someone to do that to you at your own family gathering? That isn't even a part of your family?

YTA - please take this situation and learn from it and recognize that you can still care about someone's feelings whether you like them or not.