My wife too has had issues with eating disorders and body dismorphia, and they sill bug her and influence her from time to time. She has a handle on it for the most part, but she has her moments.
And the first post is kinda right about encouragement and loving words not always working or getting through.
But I do it anyways. Because sometimes it does get through, and it'll calm her down and giver some peace.
Professional help is the way to go though. As well as you supporting her however you can; read books, attend appointments. You have quite a situation, pregnancy and her eating disorders.
I'd read some books on both subjects, and try to get her to see how this all affects your baby. Continue being supportive and encouraging. I bet there's at least one book, one support group, one person who has also been through this or witnessed it.
Good luck friend.
The Recovery Mama Guide to Your Eating Disorder Recovery in Pregnancy and Postpartum https://www.amazon.com/dp/1785928295/ref=cm_sw_r_apan_glt_fabc_YYBBSNQDVB91VP6K743G
The Clinical Guide to Fertility, Motherhood, and Eating Disorders: From Shame to Self-Acceptance https://www.amazon.com/dp/1138542237/ref=cm_sw_r_apan_glt_fabc_NDEQRKD4MK4B0S6JFQQ9
How to not let an eating disorder ruin your pregnancy https://www.amazon.com/dp/B096ZQYMY6/ref=cm_sw_r_apan_glt_fabc_4M2Z4128QC8X7XXAWFP7