I totally agree with your points and to me it sounds like she is jealous of your business.

IMO it is time for a parting of the ways.  Its sad when things like this happen but you have to look after number one.

Thanks for replying Lady, I am just sad that she felt the need to be sly about it and wish she had told me rather than confronting the client, which is embarrassing and so unprofessional. I can only imagine what he thought 
She tends to get very bolshy with people (men) when she thinks they are pulling a fast one on her, in the past it has never affected me, however this time it has, and I won't allow it to happen a second time.

The client knows we are friends, and was possibly using that to play us off against each other as well, and it has worked well if such was the case.

Either way we are escorts and no one client belongs to either of us, maybe that is the trap she is falling into. My attitude has always been I am glad one of us is getting the client, doesn't matter which one...

But yes you may be correct, a parting of the ways may be a coming as I am fuming over her actions and since she cant recognise what she has done wrong, then I feel it's impossible to move forward with her in my life.

Curvy, this may not be the first time this has happened although it is the first time you have found out.  How many other times could she have done it, no one bar her will know.

You are correct in thinking that clients dont "belong" to anyone but obviously the other person doesnt. 

She wont last long in her business if she carries on in this matter.  No one will want to see her. 

Jesus, if we don't stick together as girls, then what hope do we have XXXXX

I think it's a bit of a rush to decide to cut ties with this girl completely over this. It's unfair to criticize how she runs her business beyond this time where it has affected you. I think the best bet would be to lay down ground rules with her, eg. 'please don't discuss my business with mutual clients', if these rules weren't already agreed up on then I think it's fair to give her another chance. Find out what things she's okay with and you're okay with and start afresh from there. It's hard working in what she obviously sees as direct competition with someone if her confidence is suffering atm she's likely assuming you're more appealing than her that there's something wrong with her and she dealt with those emotionally badly and confronted the client, it's hard not to take clients choices personally, you don't know what he said to her or how she was made to feel. What she should have said was 'I no longer want to offer a discount accept my full price or leave it' but it's hard to leave it at that i'm guessing the client badgered as to why etc. Admittedly she shouldn't have offered it in the first place but once she had it was probably hard to retract it without admitting to why she wanted to.

I think the best tact would be to go in as supportive, remind her as to the importance of her boundaries and that this unfortunate event was likely the consequence of her letting them slip. If you go in supportive and consoling she'll be less defensive and you can address why you're upset and she'll more likely be open to taking it seriously. At the moment she feels like a victim, that the customer was taking the mick and for some reason you're now mad too when in her eyes she probably thinks she helped you ditch someone she perceived as a bad punter. She's in the wrong but currently she can't see that because she'll still upset.

If she doesn't agree on not doing that again etc. then maybe just be friends outside of escorting and stop working together that could still function fine, life can get lonely fast and there will always be rough patches with friends/bfs sometimes if it's worth riding it out a few weeks because the pay off for your happiness is worth it, ofc if she continues to make you miserable don't but give it time to clear first.