<human>: Can you provide a brief overview of the text?

My girlfriend requested me to be honest with her when she asks me if I am okay, I have the bad habit about lying and saying that I am O.K. when I feel like utter shit. She says me being honest is healthy communication practice between us.
She was out with her family today to celebrate her sister's birthday tonight when she asked me if I was okay and I was acting off. I did my best to be happy for her but lately my depression has been a lot worse and I was honest to her about it.
I stayed in bed for a few days because she was busy and when my friends hung out online, they'd hang out in large groups and that gives me anxiety. I told her this exactly, and her sister and mother took her phone from her, read our messages, and then her sister sent me a text message.
"I'm spending time with my sister for my birthday, can you chill the fuck out and stop making her feel like shit for spending time with me? Greatly appreciate it."
Initially, my response was "Yes, I'm sorry" but i've begun to wonder whether or not that was even acceptable.
1) They took her phone without her consent and snooped through our messages
2) They were emotionally involved in a relationship they're not a part of
3) They took the extra step past forming an opinion to shoving it down my throat.
What do I do? Am I in the wrong? Am I personally flawed? What do I change? Should I not tell her when I feel bad?
<bot>: Sister sent me her opinion of my actions after snooping through my girlfriend's phone, I do not appreciate this but cannot help but feel like shit.