The reason that the dependencies is slow is due to the number and complexity of queries that sql sever runs in order to show you a nice hierarchical structure.
There are some ways to get the data you need which vary depending on the version of sql and how much info you are looking for.
Taken from Microsoft Docs - View the Dependencies of a Table
USE AdventureWorks2012;
GO
SELECT * FROM sys.sql_expression_dependencies
WHERE referencing_id = OBJECT_ID(N'Production.vProductAndDescription');
GO
Obviously you'll need to change the AdventureWorks2012
to your database and Production.vProductAndDescription
to your Customer schema and table name.
The above works for the latest sql server editions, for older editions you may need to refer to the following links:
MSSQL Tips - Different Ways to Find SQL Server Object Dependencies
MSSQL Tips - Listing SQL Server Object Dependencies