How old is your SD?  How often is she in the home?   It's difficult to have a child not related to you in the home.. kids ARE annoying.   Every living single child in the whole world is annoying at one time or another and usually on a regular basis.  We are not hard wired to care about another person's child.  Why do so many people cringe when kids are in a restaurant.. or on a plane?  Because other people's children are annoying.period.

But, people's bio kids?  They are not as annoying and there is that uncondional parental love bond that softens the irritations.  So.. you complain to your DH about his daughter.. talking too much.  He thinks that's harsh (and depending on her age.. maybe it is) and he defends her because she is a bio child and whatevery they do is nowhere near as bad as other kids' actions.

When she interrupts... what do you do?  Do you correct her?  I don't mean in a punishing fashion.. but a matter of fact.. "honey, adults are talking now... I will answer your question when we are done.  Go to your room and I will come in a few minutes to talk to you about whatever you wanted to talk about"

Teaching her to only interrupt in emergencies.. (like a fire or injury).. is part of what kids need to learn.  They also need to learn the social norms of conversation and how to participate or not appropriately.  It doesn't require yelling or punishment.. but it does require consistancy. 

Your DH also needs to be on board with it and you need to be treating your bio equally in this regard.  When you are talking with him.. she needs to learn how to appropriately indicate that she has something she needs to ask.  He also needs to say "honey.. I will talk after me and SM are done" etc...

I so get where you are coming from. I started taking bioson out and about when SS is over, or simply staying in the bedroom which is the only room I can get away from him in. HE IS NOT ALLOWED IN OUR BEDROOM. EVER.