I’m so sorry about the hard time your daughter has had but am glad that she has been getting help and appears to be on the road to recovery. There are several issues that you’re dealing with in regards to this college search process (her drive/perfectionism, the twin, etc.).
With respect to her drive/perfectionism, I would suggest changing the framing. Rather than knowing/reciting her excellent grades (particularly remarkable with a 3-week absence), I would have all discussions reflect about what she learned in the classes (either about the subject, or the teaching style, or about ideas brought up by peers or how peers do things differently, etc). She can see that the family still cares about school, but it’s not about the grade but about what she’s getting from her classes and the experience. And that should be the case not just for her but also for her twin (and any other siblings who may still be in school). Hopefully that can start to decelerate the pressure she feels, and if family conversations remain non-grade focused for the remainder of schooling, it may help her and her sibling(s) to de-emphasize that part of school and the pressure that can come with it.
With respect to the college search, spring of junior year is often a time when the search process starts to ramp up and your daughter is bringing it up herself. I would speak with her care providers to see what they recommend. I have known people who find it very beneficial to have something outside of their area of concern to focus on, so it could be of benefit to her. But her care providers would certainly know best.
For the college process, I learned here (and think it’s a terrific idea) that it’s best to start the college search from the bottom. Meaning, finding the schools that are extremely likely to accept you that you can afford and that you would be happy to attend. That’s where both twins need to start their search, which might help ease the competitiveness.
Also, there’s this post by @CMA22 that I absolutely love and think is great reading for all who are looking for a college: How do I break the prestige mindset? - #43 by CMA22. There was also a recent thread with an update about the daughter’s college decision and how it has turned out: A look back at D22’s choice one year later and what makes a school the “best”. Thinking about some of those questions may help influence how your children approach their college search.
Wishing you and your family the best.