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Hi sir,
Could you check these sentences and tell me your opinion.

Chris says that he will bring his girlfriend to the party on Saturday.
or
Chris says that he will take his girlfriend to the patry on Saturday.

Alice says that she is planning to bring her guitar to play with us.
or
Alice says that she is planning to take her guitar to play with us.

Thank you very much...
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Chris ... will bring his girlfriend ... OK.
Chris ... will take his girlfriend ... OK.

Alice ... bring her guitar ... OK.
Alice ... take her guitar ... OK.

The speaker considers himself (or imagines himself) at the destination (of Chris and his girlfriend or of Alice and her guitar) when "bring" is used.
The speaker considers himself (or imagines himself) elsewhere -- not at the destination -- when "take" is used.

Hope that helped. Emotion: smile
Comments  
The only difference is in formal and informal writing. Generally, to bring something somewhere is to move it toward a point of action or request. To take something is to move it away from that point. When the point of action or request is not the destination itself, it depends on the context of the sentence, i.e., Alice says that she is planning to take/bring her guitar to play with us, as you have stated. In my opinion, both transitives work well in any case.