Advice to help my sister with an ED
My sister (21F) developed anorexia when she was a teen and was in treatment to recover until two years ago because she didn't like her therapist/psychiatrist (which I didn't mind) and was supposed to find another one but never settled on one. She returned back to a healthy weight some years ago but was still in psychological treatment, she abandoned treatment completely when she wasn't feeling ok mentally. However, three years ago she was overall ok, I thought that when she felt bad it was part of her healing (since recovery isn't linear) but I couldn't know exactly because she has never opened up to anyone in the family about her feelings/emotional state.
She has relapsed for around 8 months now? (I'm really bad at tracking time) She is underweight and back to unhealthy habits. She completely denies this to everyone and tells us we want to control her and that we watch everything she does and wants to be left alone. Whenever I try to bring this up when we're alone she tells me the same and that she is already stressed with her studies and doesn't want me to stress her anymore than she already is. But I just don't want her to get worse and end up in a hospital bed or dead.
I consider our relationship isn't like normal sisters anymore partly because of her ED. While she never wanted to talk to me about her feelings, I sometimes would open up to her and overall talked normally but lately there's always a fight in the house (whether with me or my parents) because she refuses to at least admit she's unwell and we're concerned about her. I admit my family was never perfect or even normal because my parents tend to be very toxic and I can see why she's stressed but denying everything only worsens the situation. It's childish, but I don't feel it's worth opening up to her when she is so cold to me now.
I (19F) also developed anorexia shortly after my sister developed one before and was also in treatment shortly after. I think it's worth mentioning at the time I also denied it but my sister kept insisting that I should get treatment (whether it be because I was triggering her or because she was concerned). I remember I was mad at her at the time, but now I partly understand it was for the best, so I would like to help her too. However, it feels impossible because her reactions are more extreme than mine at the time. If you insist she starts crying and shouting, saying we're just imagining things. But I know something is wrong because I recognise the patterns. I'm worried that if we force her too much she will harm herself because, when she first developed an ED, she used to threaten to kill herself whenever we told her she had to do x thing to get better and I believe her mental health right now is almost as fragile as back then.
Her ED has also caused my mental health to worsen because I am constantly getting triggered by almost everything she does and I honestly hate coming back home after classes because I know she will still do the same. I've never told her this because I don't want to make it seem I'm victimising myself, I only want her to know I'm concerned for her health, both mental and physical but nothing seems to be working. I am writing this here because I am lost at how to approach the situation and thought others who are going through an ED at the moment can help with their perspective.