<human>: I am a 33/M and have two half-sisters who live about 2,000 miles from me (I moved away when they were 10 and 7). Older (Kelly) is 19 and younger (Julia) is 16.

Overall they (including my dad and stepmom) and I have a friendly but distant relationship. We see each other about once a year. They're very religious and mostly conservative-minded, I'm a leftie and I suspect they know I'm not religious at all. They homeschooled their kids but tried to offset potential social weirdness by getting them heavily involved in a mainstream church, dance lessons, camps, Girl Scouts, etc.

Kelly, the 19 y/o, is a social butterfly, but the 16 y/o (Julia) is, at a minimum, much more introverted and spends most of my visits home in her room on her laptop.

This sounds a lot like your typical teen, but Kelly shared with me that Julia has pretty intense social anxiety, and I don't know if the family is addressing it. Mental health hasn't been an issue for anyone else in that family unit, but it has been for me (different mom). I dealt with awful social anxiety on and off for years, and have only in the last couple of years adequately addressed it with therapy and meds.

What's worse is my stepmom basically doesn't believe that depression/anxiety is a real thing, and my dad knows better but is easily influenced by her.

I want to help simply b/c I wasted years of my life depressed and anxious before I made a sustained effort at getting better. I don't know that Julia even knows how to put into words what she's feeling, or that it can be treated effectively.

Provide a brief overview of the text.
<bot>: How can I help younger sister with social anxiety while living far away and ideally not offending family that doesn't believe in mental illness?