thvnndr

Also having this issue and its insufferable. Come on Squarespace, for what you're charging this should be simple... 

Hi Colin, 
I'm sorry this is such a late reply, it has been a super busy week! Thank you so, so much for taking the time to have a look, and for the kind and helpful feedback :) I truly appreciate it! 

I will definitely pop this on Analytics, that's a really good idea. 
Hope you have a wonderful week!

It looks fine to me. Tested on a pc laptop, 1920 x 1080 screen resolution (but I resized the browser width narrower to test). Tested on Chrome and Firefox.  
Also looks good, great in fact, on iPad Pro. 
Ask the designer who contacted you to provide details of the operating system, screen res, browser, etc that she sees the problem on. Ask her to provide screenshots or better still a screen recording. 
If the problem is at some weird screen width, don't worry about it. Most people don't dynamically resize their browsers looking for problems. 
Also, if you need to justify this to a client, install Google Analytics on the site and let it collect data for a week or so. Then look at the reports on screen dimensions, device, etc to work out how many people are actually experiencing the problem.