Nearly all personal letters between unrelated people of the same gender, but especially of women, before about the early 20th century (and very many after) read as seriously slashy. Most of it is probably just that they were more open about expressing affection and emotional need than we are. But some of it is also... well, for the obvious reason.

I love the early 18th century. It was absolutely prime for gossip and their worldviews are easy for us to understand today.