Hi Shanc and welcome to the forum.
Certainly the things you mention strongly indicate BPD. If you have a good psychiatrist, then you're lucky. Firstly, you got a diagnosis and that major issue for those with BPD. For some, it seems to happen quickly, however I belong to a Melbourne based group of BPD sufferers that hold monthly meetings and practically all our members have been very slow to be diagnosed. It's a common thing because of the stigma. I had to practically scream at my GP to tell me what was in the report from my psychiatrist and even then he asked what difference it made to know and went further to add........"You can't change your personality!"
He's old school and obviously doesn't know a lot about BPD. Modern thinking has the personality as a more fluid thing than was first thought, so it may be possible to alter a poorly functioning personality. The woman who runs our group is a classic example of someone who was told they'd probably spend most of their life in locked wards, only to get her life together with the help of an amazing friend and DBT. She's not perfect, but the transformation has been profound. If you're interested, you might like to use a search engine to look up the group. I'd post a link here, but it would probably break the community rules 
We also have a BPD forum which you might like to join.
Your mum sounds unfortunately typical of the same "old school" thinking as my sister, who is ten years older than me. Mention anything to do with psych and I see the shutters go down behind her eyes. She just doesn't want to know because she thinks all I have to do is get a grip and soldier on. All the while, she has her own set of problems and refuses to recognise them.
As to cutting off friends, yes, that's something I do quite freely. It's the old love/hate thing for me. They only have to say the wrong thing and I go from great admiration to total disdain in a heartbeat. Their words, even though they might not be meant at hurtful, wound like a white hot sword. People just don't think, but then again they're not trained to talk to people suffering BPD. The don't realise that a simple little gesture or word can set of an emotional avalanche.
Oh, one thing too you may not be aware of, your BPD symptoms probably won't match everybody elses in text book fashion. Using a combination of the 9 criteria for having BPD, there are 256 variants, so rarely will you find two sufferers with exactly the same set of symptoms.
Some of the above is probably out of context, but it's the best I can do at present.
Kind regards,
Ellie.
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Help us push aside the stigma and discrimination surrounding complex mental health and change the way people talk about, and care for, mental illness.
SANE acknowledges the Aboriginal and Torres Strait Islander peoples as traditional custodians of the land on which it operates. We pay respect to Elders past, present and emerging, and value the rich history, unbroken culture and ongoing connection of Aboriginal and Torres Strait Islander people to country.
SANE values diversity. We are committed to providing a safe, culturally appropriate, and inclusive service for all people, regardless of their ethnicity, faith, disability, sexuality, or gender identity.