Egg whites are not vegan. A vegan is defined as a person who avoids all kinds of products that involve exploitation and cruelty to animals in some way. Vegans never include any animal products in their diet even if no animals were killed to make them.
 
Commercial egg production employs various practices that harm the birds, and denies them the right to freedom and life. Egg white is the clear part of the egg that is not vegan. You get vegan egg whites in the market but they are not made from real eggs. Manufacturers use plant-based ingredients that have similar properties of egg whites to make vegan egg whites that are popularly used as replacement for egg whites in vegan recipes.
 
The commercial poultry and egg industry have been infamous for the cruelty towards birds. They are kept in poor conditions throughout their life and are sent to slaughter once their egg laying capacity declines.