I’m sorry to hear you hit a snag while helping your student with their design in Inkscape. The centerline trace option which others have mentioned is only available with an add-on to the program, but there might be other options you can try.
A great resource on the forum is our Community Glowforge Tutorials: Table of Contents. On that page, you can find a link to the 2D Software Matrix. This would be an excellent place for you and your student to look for help with a variety of topics.
Based on what you’ve described so far, these post from other community members in particular might be helpful:
A method to create offset outline around a bitmap using Inkscape
Breaking up a large design (Inkscape)
Will these help you get closer to your goal?