Personally, I would use the pronoun that's being used for present events. I've heard a few people say that sometimes when they imagine themselves as children, they remember themselves as the gender they are now even though they know that's not how it was then.
It also makes things way simpler, which is another reason why I like it. If you respond to 'she' and 'her' now, why not use them to refer to the younger version? It's easier to keep the stories straight when there's only one to deal with.