3 feet are in 1 yard and her fence is 25 yards long so her fence is 3*25 = <<3*25=75>>75 feet long
At maturity these trees will measure 1.5 feet and she needs them to run along her 75-foot fence so she needs 75/1.5 = <<75/1.5=50>>50 trees
The trees cost $8.00 apiece and she needs 50 so 8*50 = $<<8*50=400.00>>400.00 worth of trees
#### 400