best way to remove shadows from under the eyes of my model in Lightroom

You can do it in seconds, as shown in the demo below. Just add a mask group containing two radial gradients, one for each eye. Apply a single positive Shadows adjustment to the mask group, and you might be done at that point.

(Although you can optionally customize the mask shape by subtracting a Brush mask, or apply other mask adjustments such as Exposure, Whites, or Blacks as needed. Or further isolate the shadows by intersecting the mask group with a Luminance Range mask.)

The image has other lighting problems, though. Notice that when you see the entire image at Fit magnification, there is a large and distracting hot spot on her chest. You will want to tone that down with a separate mask, such as a Radial Gradient set to a lower Highlights or Exposure value.

The Masking icon with Brush Tool (for exposure adjustment), and or, the Healing Brush Tool, should help you achieve the result you want.

This video might be helpful (although made with the 'other' Lightroom.)

portrait eye masking brush in lightroom