You can pass a name to Faker::Internet.email
to generate a fake email address for that person. You'll have to do a bit more work but not too much:
first_name = Faker::Name.first_name
last_name = Faker::Name.last_name
person = Person.create(
:first_name => first_name
:last_name => last_name
:email => Faker::Internet.email(first_name + "." + last_name)
)