Hi @Chantelle_Crawford, Happy Monday!
Thanks for reaching out.
Great question, it seems the team member has two separate Asana accounts (one linked to the Guest’s email address and one linked to the company email address).
What I recommend her to do is to merge both accounts. By doing so, only one account will appear when you assign them a task.
You can find more information in this thread: Merge 2 Asana Accounts? and this Asana Guide article.
Let me know if you have additional questions. Have a great day!