Help with Email & Changing Name Servers/Webhost?

Alright, time to ask for help. I designed a website for my cousin using Wordpress, hosted via BlueHost. It's 99% done.

The problem: she'd originally registered her domain through wordpress.com. She also has an email through that, which she accesses via Google Workplace. We've transferred the domain, but the nameservers are still registered to wordpress.com. I've found the guides for transferring nameservers on BlueHost and wordpress.com, but this is a step above what I've dealt with in the past.

My main concern and frustration are the email. She's already using it for work, and I want to make sure there's no downtime, but I... honestly have no idea how it's even set up, right now. Or how this would work when transferring hosts entirely. Attempts to search it haven't been too helpful for me.

So my questions: How will changing nameservers impact the email? Would updating them potentially just... break her email entirely? Need her to set up the email separately? And if she does, can it be kept through Google Workplace/Gmail since that's what she's already using? Is it fine to leave it as-is? I assume not but her wordpress.com account shows that it expires in 2027, so...?

Just, please help.