You have a choice. You could use the UV absorbance, which will be a combination of the absorbance of the protein and the fluorescein at that wavelength. or, you could use the 495 nm absorbance due to fluorescein alone (which is not UV, by the way, it's visible. Fluorescein has a greenish-yellow color). Or, if you need greater sensitivity and have suitable equipment, you could use the fluorescence of fluorescein, which is at least 100 times more sensitive than the absorbance measurement.

Dear Adam, your answer is much appreciated and would be a suitable guide for my experiment.