Spinel isn't anything specific. She's like Jessie's story on Toy Story. It's a universal human experience to have people drift out of your life. Sometimes it's more extreme, like a deadbeat dad taking off, having your wife leave you, or even both parents straight up abandoning their kids in a ditch somewhere. But low key versions with people who just lose touch and one person feeling hurt are just garden variety everyday things, that's why everybody can relate to them. Neglect in relationships and by school/work are also ubiquitous.
If anything, current Spinel is a little bit BPD, Borderline Personality Disorder, not bipolar. This tends to be characterized by abandonment issues, clinginess, and "splitting" where the most important person in their life is either a perfect angel or a vile demon or it flipflops. But she's a gem, she doesn't have BPD in the human sense.