Hi moh2025 and welcome to the boards

You're at a good starting point for a journey of learning and personal growth. For so many of us members, we showed up here asking "why does s/he do that?", and we're moving towards "why do I do that, and what choices can I make" -- really getting personally empowered

Education and learning more about BPD (sometimes called CED, or "chronic emotional dysregulation") is definitely part of that journey.
A great reputable source for up-to-date info about BPD/CED (besides us here!) is the
National Education Alliance for Borderline Personality Disorder. Their
overview of BPD highlights some stuff that seems to apply to your situation:
Borderline personality disorder (BPD) is a serious mental illness that centers on the inability to manage emotions effectively. The disorder occurs in the context of relationships: sometimes all relationships are affected, sometimes only one. It usually begins during adolescence or early adulthood.
While some persons with BPD are high functioning in certain settings, their private lives may be in turmoil. Most people who have BPD suffer from problems regulating their emotions and thoughts, impulsive and sometimes reckless behavior, and unstable relationships
Other disorders, such as depression, anxiety disorders, eating disorders, substance abuse and other personality disorders can often exist along with BPD
How can you best explain her intentions and psychology?
From my perspective, it's critical to remember that if we suspect BPD is in play, then we need to remind ourselves that it's a real, serious, and profoundly impairing
mental illness. We can't both think "it might be BPD" and also ask "so there must be detailed, logical, and rational explanations for his/her behavior".
Maybe one way to approach the question is -- what she's doing makes sense
to her in the moment that she feels whatever she's feeling. If BPD is indeed in the mix, then she may struggle with intense, overwhelming, out of control emotions, and much of her focus will be on trying to feel OK inside... and very little of her focus or planning is on "how can I make him feel/do XYZ".
NEABPD has a little more to fill that out:
What does “Borderline Personality Disorder” mean?
Historically, the term “borderline” has been the subject of much debate. BPD used to be considered on the “borderline” between psychosis and neurosis. The name stuck, even though it doesn’t describe the condition very well and, in fact, may be more harmful than helpful. The term “borderline” also has a history of misuse and prejudice—BPD is a clinical diagnosis, not a judgment.
Current ideas about the condition focus on ongoing patterns of difficulty with self-regulation (the ability to soothe oneself in times of stress) and trouble with emotions, thinking, behaviors, relationships and self-image. Some people refer to BPD as “Emotion Disregulation.”
So, her intentions may be 100% self focused, and her psychology may be 100% about trying to regulate, in low-skilled ways.
...
A couple good questions for continuing on your journey of growth might be found here:
She insisted that she just wanted to be friends with me, yet she and her friends had issues with my girlfriend after. Her brother, and other people still keep tabs on her for me. And her friends in her home town still interfere with me getting to know other women despite her now being married and having a newborn. Like she is almost territorial about me but has no interest. I imagine that after we both started to date other people things would change but the drama persists today.
Having family keep tabs on her for you seems like a choice that's under your control. What do you think?
How are her friends seeming to interfere with your relationships? Are there some options there under your control?
We often have more control over our trajectories than we think

Glad you landed here... looking forward to learning more of your story;
kells76