She uses 3 ounces of beans per day because 2 x 1.5 = <<2*1.5=3>>3
She uses 21 ounces of beans per week because 7 x 3 = <<7*3=21>>21
She buys 2 bags of beans per week because 21 / 10.5 = <<21/10.5=2>>2
She spends $16 on the beans per week because 2 x 8 = <<16=16>>16
She spends $2 on the milk per week because 4 x (1/2) = <<4*(1/2)=2>>2
She spends $18 per week on her coffee because 16 + 2 = <<16+2=18>>18
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