I have a sister who tried to commit suicide when I was a teen.
I grew up in a household a bit like Elena's. While my sister got help, it was not discussed.
My sister is still messed up to this day.
I think, if it were me, I'd see the show, and like any good movie or show, talk afterwards - of let her talk - and you listen. Answer questions - but just let her know she can talk/and you'll listen and answer questions as best you can.
If you can relate at all to the subject matter - all the better. Kids love that. That's how I bond with my teens. I screwed up (a lot) and my family went through the ringer and so they love to hear these stories (I don't share everything mind you...) - but they like to know that I'm human, and that I'll be very understanding and accepting. So if you can bring up something about mental health - yourself, a family member, a friend .... that might be a good way to relate to the show.
I think the main point to get across is that you're there - if she needs you, or she runs into a situation where she needs to come to you with something that worries her. Mental health issues can be scary - because people still don't like to talk about them.