It sounds like you’re going through a really rough time right now. I remember how rejection is a massive trigger to you and echoes past wounds that are still very present to you. I would like to encourage you to see the situation as it is though: objectively hurtful, but also a situation that acts as an emotional trigger to you. It is leading to powerful thoughts about yourself, about others and about the world in general. It makes sense why it is there, although to navigate this pain and heal as well, it will be important for you to acknowledge the difference between the facts and the conclusions it is leading you to.
Being nice and being friends, being you does not lead you to this situation. This person isn’t evil either. It’s not about her character or yours. She simply loves someone else. Her heart is dedicated to her boyfriend, so there is simply no space for someone else. It is unfortunate that your mom encouraged you to date this person because that wasn’t fair. It was, somehow, setting yourself up for disappointment and heartbreak. It sounds like there were quite some elements at play beyond your control and I’m sorry for that.
This person has her own life and deserves to be happy with the person she shares her life with. This has nothing to do with you or the quality of her heart. It is simply how it is. I am myself in a relationship with my fiance and if someone was trying to date me right now I would not be interested, whether the person would be wonderful or not, whether we would be friend or not. I could care for someone genuinely yet not being interested in having a love type of relationship. Being already in a relationship doesn’t make someone a bad person, and it doesn’t make the one trying to date unlovable. You are not unlovable. She is not evil. You were simply not meant to be in a relationship together right now. I know that hurts deeply and there is a need to find some answers. I promise you though, it’s only an unfortunate matter of circumstances. It’s not her fault. It’s not yours.
I know this hurts a lot and revives some deep wounds to you. It’s understandable to see situations like these through a good/bad opposition, to paint the world and people as either dark or not. Reality is more complex though. Please make sure to not let yourself overwhelmed by thoughts that are not true. Don’t let this pain lead you to hurt yourself or others more. Right now, you deserve to be patient with yourself, to breathe and remember that you will find more clarity once the pain will subside a little bit. You are not meant to feel this way forever, friend.
On a different note, I’d like to encourage you to reach out to your therapist in times to come. It sounds that now would be a good time to rely on them a little bit more, share what’s on your heart. They will help you discern truth and lies, what stems from pain and what belongs to facts, all at your own pace. Make sure to rely on your support system during this difficult time. Use the healthy coping mechanisms that you have learned over the years. It’s exactly during those times that you will need them the most.
You deserve to heal from this heartbreak in ways that wouldn’t be damaging for anyone. There are intense emotions at play that need to be processed in healthy ways. I believe in you and in your ability to ride these intense feelings in a safe manner. You’ve managed to do it before, you can keep doing it right now. These emotions are very real, although they are not meant to be your forever. You can make it through safely. There is true, real healing ahead.
Deep breaths, friend.