What do do if your great-aunt has all the family photos and documents but she won't let you have access to them? She won't tell you anything about the family saying only "Least said, soonest mended" in response to your repeatedly asking her for information
The first thing you should realize is that no amount of begging or asking or demanding is going to make Aunt Hattie change her mind. There are a few "tricks" you can try though!
1. Try to find out (gently) what her objection is to your seeing the documents and photos. There may be something which she considers a disgrace and if so, it will be your job to reassure her that you can be trusted. Don't lie to her though. If your intent is to share the facts with your entire family, then don't tell her you won't tell a soul.
2. Mean what you say. "I won't tell anyone else" means that you will keep quiet about whatever she shows you. Some will disagree with me but in my mind that promise only lasts while Aunt Hattie is living. After she is gone, you may have to make some decisions about sharing or not sharing what you have learned.
3. Visit or phone Aunt Hattie frequently. Not to ask questions but to talk, take her out for a meal, just sit and have tea or coffee with her. Get her talking about her childhood and enjoy her stories. Eventually she may relax and start showing you items from her treasures.
4. Take Aunt Hattie your own photos or documents - don't overwhelm her, just take one or two each time you visit. Show them to her, talk about the people and what the photos or documents mean to you. When Auntie sees your passion and genuine caring for the people involved, she may relent and share her items with you.
5. Be patient. It may take your Auntie a year or more to decide you shall be privy to the family secrets. Don't push her and don't rush her. Let her come around (if she does) in her own time and her own way.
6. Try an end run - find out who Aunt Hattie is closest to in the family and get them on your side. They can gently work their magic with her and hopefully persuade her to share.
7. Don't give up. But don't be overbearing either. In my hubby's family he had a step grandmother who would not talk about his grandfather's misdeeds - which were quite outrageous! Eventually she opened up and filled us in on quite a bit. Patience and getting to know us were the magic that worked for us.