My girlfriend and possible Bipolar Disorder?

So me and my girlfriend have been together for a year and a month to be precise, and since then, we've been through quite a lot.
I've discovered that her family don't treat her all that well and I think that has a massive effect on her, but she doesn't see any bad in them whereas myself as an outsider, can see they don't really want her and this kills me. But I'll mainly just talk about the times where I feel she may have BPD.

So from being together, I know her mum has treat her awfully and giving her abuse. But my girlfriend was living in this horrible house and me and my family invited her to come and live with us. She didn't want to at first but in the end she did. Although it was a few months later that her mum started on her again. I'd ran myself a bath until I saw her crying after a phone call, so I told her to get into it instead and relax.

I sat with her, talking to her and then she started saying she didn't want to be here anymore and was dunking her head under the water. I don't know if she really was suicidal or wanted attention but regardless I pulled her back up numerous times. It was then that she seemed to distance a little bit. She later lost two family members and that made her worse, but it's understandable. But it went on for months when she just became so angry, I'll admit I shouldn't have, but even I distanced from her a little bit.

She then got her head into some game but she was playing it from late morning until after midnight. About 14 hours each day. She knew she was returning home for the summer and to be forced to work so she was claiming she deserved a rest.

Her family aren't from the UK but she returned home in the summer, and I was invited to stay with them for the duration. At first her mum was lovely, couldn't fault her yet within a matter of weeks her mum was stealing money from her, forcing her to work 15/16 hours a day for the family business. And then it got to a point where her mum was abusing me and my family, calling me and my mum mentally ill and telling my girlfriend that me and my step dad were going to rape her. She was worried about her mum being mentally ill and from the looks of it, she was.

About a month and a half into the trip, my girlfriend just changed on me one evening. She got into this horrible mood with me. I started packing my bags and she thought I was joking but she invited me for a walk, all she did was hurl abuse at me. The one that got to me the most was when I reminded her that her mum called me a rapist, and she turned around and told me I was and that I raped her of her virginity and forced myself on her. That did it for me, I went back and continued to pack my bags. She broke down in tears begging me not to leave her and that she loved me. She said "I've been a horrible girlfriend I'm really sorry" and she was on her hands and knees begging me. I didn't go. But I did return home when I was supposed to and she was getting funny with me over Facebook plenty of times.

When she returned back to the UK, she became completely different. She became so angry, so lazy, so unenthused about her future. She used to be so ambitious about university and she's spending her time doing other things when I try to push her to do her work, and then she's upset when she's getting low grades.

My family are getting stressed due to her not helping around the house and she's just living here rent free. She's only just found a job, but it's more the fact she just sits in bed all day playing games or watching videos and rarely socialises with my family anymore or helps with chores around the house. My step dad suggested bipolar to me a few weeks ago and it got me thinking. But then a few days ago she just turned on me after a week of being so happy and enthused with herself. It was then I thought of it myself. And realised something isn't right.

I was reading other forums where a guy said his girlfriend (with suspected BPD) is accusing him of loving other girls in which she does. But other things I've seen from websites, during the depression stages she just refuses to have sex with me and rejects me all the time, she closes herself in and plays games or whatever for a while. But during the mania, well sometimes that includes unsafe sex (I know I'm included with that but we're so intimate it just happens and I know it needs to stop) and she talks loud and fast. On Friday she was annoyed at me and didn't talk to me all day, yesterday I couldn't get her to stop talking she was that enthusiastic and happy. And then going to bed she just dropped again, saying horrible stuff about my mum just before going to sleep.

I apologise for it being long, but believe me, this isn't the half of it. I love her so much but whilst she carries on treating me like this, I can't see a future with her. I know mentally I'm not right either, I'm going through depression too but it's partially because of this, partially because I'm in the middle of my family all telling me she's treating me like a mug and she's walking all over me, when I know there's just something in her head and this isn't the real her. And then I have her badmouthing my family just because her own mum has. Each time her mum abuses her, she's all over me but then whenever her mum is nice again, she can't ever do any wrong.

I try to talk to her and even my mum suggested I get her to the doctors but she can't see herself as not being right. She opened up to me last week and admitted she's changed a bit but I can't see her changing back any time soon..

Any advice?