I think it is unfair to assume your wife lied to you versus did not think to include that instance, especially if she had more sex than you did in her past.

What interactions mean something to us is an individual thing, you, for example, put a great deal of emphasis on sexual acts of others you are contemplating being intimate with whereas another person might not because another person would have a different background from yours. That does not mean that your interpretation of their response is "better" or more true/correct than what they say, she has said she didn't remember it at the time and I would be inclined, were it my husband, to believe s/he did not remember it at the time!

I think, if she were so worried about your response then, that she "lied", she would be no less worried about it now that she would tell you; I think she would have made up with a different answer to your recent query. If she knew how you were then and it bothered her enough to lie, she should be able to know how you are now, that it would bother you and keep on lying.

There's nothing "unfair" about her having had this experience and you not knowing so marrying her on "false" pretenses; you can still divorce her now just as easily as you could not have married her then if it disturbs you the same way. If you have not changed and grown in loving your wife that her past still bothers you, I would not stay with her. As you say, if you believe she lied, she could have lied about anything/be still lying and you really don't know her/she's not who you supposed/want to be with. You are still a free agent to decide what you like/do not like and what to do about it, if anything. The not being able to look at her is not because of her behavior, it's inside you and your background/thoughts and feelings. She cannot effect/change that anymore than you can change hers.