Female friend sleeping over at my boyfriends house?

Im in a new realationship, and my boyfriend has a very close female friend. She is great and i really like her. His parents was on a vacation durring one week. My boyfriend invited some friends over the first weekend, and that female friend sleept over at his place (not in his bed).

I thought it was okey since she was to drunk to drive home. But she ended up staying the WHOLE week. He told me that they are just friends, nothing happend and that she does that sometimes with other friends. For me this is unaccepteble and it dont matter that ”nothing happend”.

What should i do? Im seriously considering leaving him. What should i say? (Sorry, English is not my first language)
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Try to talk about it?
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Female friend sleeping over at my boyfriends house?
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