Advice for my mom who has a Master's in Economics and is ABD for a PhD

[Duneranger]

Hi everyone. First of all, just wanted to say that forum helped me to finish my bachelor's degree in computer science at TESU - just walked this September. Thank you!
My mother is in her 70s and has always wanted to finish her doctorate. She earned a Master's in Business and Economics in France (where she's from). Then she went to the University of Pennsylvania as an economics PhD student in the 1970s, and earned a master's in International Economics and Economic Development on the way to the PhD. She then finished all the requirements to earn her PhD - coursework and comprehensive exams - but she never finished her dissertation.
My question is, what's the best and easiest way for her to finish her doctorate? Should she reach out to her original university - U of Penn - and try to re-enroll, find an advisor, and finish her dissertation? Are there any doctoral programs in Business or Economics that would accept transfer credit from the 70s? She's older, so I'd rather she not have to expend a huge amount of time and energy to finish. Let me know if you have any questions to help clarify things. Thanks!

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The dissertation is like the biggest chunk of a PhD program since it’s a research based degree. It could take years.

Costs at UPenn would be crazy since I doubt it would be funded.