hey @ComaToes our mind and body can be pretty interesting, hey. sometimes it stores onto memories and emotions and decides to release it years later! i have heard that sometimes it happens because our mind/body isn't ready to process or doesn't feel like its safe enough to, so it saves it for when we're ready to face it.
it's interesting how something from 50 years ago has popped up now! i definitely hear where you're coming from, the curiousity to know how she's doing and what she's up to can be so tempting. but at the same time, some people might find it intrusive and may want to keep the past in the 'past'. it depends on the person of course, so it can be hard to tell! i guess something you can think about is, what do you want to get out of the interaction? what happens if she isn't happy/content? is this going to impact your current relationship? will this impact your mental health? etc.
sometimes it can be better to accept and let go of the unknown, and sometimes getting answers are important - it's a hard choice to make! speaking to my psych helped me heaps in making my choice. what does your partner think about this?