Hey @SeahorseUnicorn, thanks for reaching out to us.
It sounds like the folder you're trying to share with this person, is larger than their available space.
Shared folders take up space in each member's account, when they have edit permissions.
If you want to share a folder, without affecting their Dropbox space, you can share a "view-only" link with them instead.
Let me know if you have any questions.