Maybe she's afraid you'll get stuck in the past and/or are using it to avoid talking about other things?

When my ex-T. and I had the same issue, I realized I didn't feel heard. It's not that she couldn't say "hey, we need to go this direction" but I never felt she really heard what I needed. So, maybe it would help if she said "I hear that you would like to ______ but this is why I think this direction is better. Or maybe you could compromise on doing a little of past and present?