You've opened a big can of worms here.
Being that it was her first boyfriend and she is young, she is probably having a hard time letting go. If she is still in contact with him through emails, lunch, etc, then she is probably not over him and it will either drive you or make you crazy.
At least she did tell you she had lunch with him, she could have kept that a secret from you. Stop seeing her or paying any attention to her for awhile. He who cares the least will win out.
