13 months and minimal solids?

My daughter is starting to have projectile vomits again. She was better and all of the sudden last week she’s just getting difficult to feed again. We are seeing feeding therapist but she is only taking 4 ouces of yogurt and maybe 2 ouces of baby pure food and that’s struggle for her. Anyone out there that has a baby that’s over 13 months and still rely heavily on formula? She’s on 24 ouces of Nestle Good Start and 8 ouce of pedisure everyday and she’s skinny to the bones. Her twin brother is 21 lbs and she’s only 17 lbs.