Load google font script based on optgroup label selected

Ive searched and can’t find an answer. I have two groups of fonts – one regular fonts and one google fonts. Im using a select dropdown list with two optgroups, one for each group of fonts. What Im trying to accomplish is to load the script for google fonts on the front-end only if a font is selected under that optgroup label. Im able to get the value of the font-family selected in the option, but not the optgroup. I’ll attach a screenshot of the dropdown in the admin area.