Hello Pam: I believe this is your first thread here on PC. So... welcome to PsychCentral. There is a forum, here on PC, dedicated to the subject of BPD. It may be helpful to you to read through some of the posts in that forum. Here's a link:

https://forums.psychcentral.com/bord...lity-disorder/

And then here are links to 13 articles, from PsychCentral's archives, on various aspects of BPD, & helping someone who has it, that hopefully may be of some help. Some of these may be helpful for your granddaughter to read as well should she wish to do so. (Perhaps she'll wish to become a member here on PC herself at some point.):

An Overview of Borderline Personality Disorder

Understanding Adolescents With Borderline Personality Traits

Treatment Options for Teens With Borderline Personality Traits

Living with Borderline Personality Disorder

https://psychcentral.com/lib/how-to-...dium=popular17

https://psychcentral.com/lib/how-to-...dium=popular17

https://psychcentral.com/lib/the-emo...dium=popular17

https://psychcentral.com/blog/free-l...dium=popular17

https://psychcentral.com/blog/6-gift...dium=popular17

https://psychcentral.com/lib/dialect...isorder/?all=1

https://psychcentral.com/blog/helpin...dium=popular17

https://psychcentral.com/lib/the-ess...lity-disorder/

https://psychcentral.com/lib/stop-wa...dium=popular17

I hope you find PC to be of benefit.