Rainbow Diamonds

She's being patient with someone with Borderline Personality Disorder trying to get her to enjoy the school. I get she's loyal, but she's not THAT loyal, right? Especially if she doesn't know that the other character has BPD. Though... if Rainbow is given a challenge, she would try to be patient with her, right?

Do you remember how patient (and understanding) Rainbow Dash was with certain yellow pegasus in "Hurricane Fluttershy" [s2E22]?

She was not aware of the kind of unresolved trauma Flutters carried from fillyhood (and how incapacitated it was), until she bursted in tears and run away from the testing grounds.

Another great example of "Loyalty through sickness" is the lack of vitality of Tank in S5E05 (before she accepted the true nature of the "sleepy syndrome" he had just developed). Her attempts to find an "indirect cure" [much like removing the source of an alergy] is a sign of her determination to help her loved ones.