<human>: Can you give me a shortened version of the text?

Typing this on my phone, so I apologize for awkward formatting.    

My boyfriend's sister is in town visiting (she lives in another state) and last night was my first time meeting her. She and my boyfriend are very close, so I really WANT to like her and get along with her. Maybe I just need to be around her more, but last night left me very concerned about my ability to do so.    
I was raised to never ever interrupt someone while they are speaking. I was taught (rightly so, in my opinion) that interrupting someone is incredibly rude and disrespectful. With my boyfriend, this has literally NEVER been an issue. His sister... not so much. I am not exaggerating when I say I did not get to finish speaking even ONCE last night over the course of several hours  - many times I couldn't even get 5 words out before she steamrolled me.  
I'm trying not to take it personally, since she exhibited this same behavior to other people present - I wasn't singled out or anything - but I need help dealing with it. My boyfriend, since they're siblings, just interrupts her right back with "no no no, wait, let me finish" but I'm not comfortable doing that since I don't know her well at all.    
The experience left me incredibly frustrated and spending the next week with her now seems daunting and unpleasant, even though she's a generally friendly and gregarious  person.    
Has anyone dealt with a similar situation? How do I stand up for myself without sinking to the same rudeness? I know I need to speak with my boyfriend, but how can I do so without hurting his feelings?
<bot>: met boyfriend's sister for the first time, and she is visiting for the next week. She is friendly, but a chronic interrupter and I need some advise in being heard.