None of Google’s iOS Apps support the Apple Pencil.
Not sure what alternative apps would work/do this for this on iOS.
Maybe look at MS Office for iOS.
If it has Apple Pencil support, to do any work on these apps, you would need to pay Microsoft’s monthly MS Office 365 subscription price.
There are other alternative methods to do what you want to do, but have NO cut and paste ability.
There are many ways to edited info in the document with highlighted areas, send the changes as an email attachment, but your assistant would need to still have to manually input the data.
You could try importing the data into an Apple Pencil compatible PDF app, mark it up, highlight areas then take a screen shot of the edited doc and send the image as an email for your assistant to alter the real document or just send a copy of the edited PDF of the document.
Or similar thing, but try using an Apple Pencil third party compatible notes app and do the same thing.
Edit the info, highlight the info and take a screenshot and email the change to the assistant that way.
OR take a screen shot first of the Google doc and use an Apple Pencil compatible third party notes app to write and markup ( or draw ) over the image to make changes, and either take another screen shot or save edits as PDF or RTF document or something that your assistant can easily see it the email.
Your assistant would still have to make such changes manually.
The advice I am giving here is very generalized, so there maybe some other steps involved or other options available.
I am just expressing a possible set of workarounds.
iPads are NOT full featured laptops.
Many times with iOS/iPads, you have to think outside of the box to get something done.
Best of Luck to You!