Should he block her?

Jules
Ok so I have this issue with my boyfriend right now and I brought it to his attention to. 
To start off a few months back I had an issue with this girl and one of her ex's message me warning me about her saying how she ruins relationships and what not. Of course I thought it was someone messing with me and I told my boyfriend. 
He told me that she was a lesbian and had no interest in him what so ever. So I blocked the dude and went on with my life. Few months later to last week on his birthday he has a "guys night" or so I thought....
I was at a drum circle so I'm miles away from home but my phone still had service. I start getting these texts from my boyfriend that says "stop saying you love me" and "I don't want to be with you anymore" and just so much more.
Then I get a pic message of him and her. That's when I flipped out and was calling trying to figure out wtf was going on. So the same girl from months ago showed up at his birthday, took his phone and was pretending to be him and the one sending me texts. 
So yea we went through all this argument blah blah blah and so now here we are and we are working together on being more honest, trust and communication. I told him that if you are really wanting to work on this then I don't want you and her talking. Like I don't want her existence at all in my relationship. 
He says that they are just friends but her whole intention was completely disrespectful and almost ruin my 6 year relationship. At the beginning of our relationship one of my ex boyfriends did something similar which resulted me blocking him on everything and I haven't spoken to him since.
So am I right to ask him to block her and not talk to her anymore?
Sorry if this was so long.