Well, I can say one thing for certain; If Acacia has a Den, then none of the Deep Forest tiles mention anything about it.
I've been trying to get around for a while now with no luck, Acacia Always finds you.
I've heard that she supposedly sleeps, yet I've not been able to find an hour where this is the case. She's awake in the middle of the day, and awake in the middle of the night. And, of course, the NPC Editor does not allow you to edit her in any way.
So, I can't say for certain, but I am going to make an educated guess.
If I remember correctly, the devs have previously mentioned that Acacia is so dangerous to justify the amazing loot you can find in the Deep Forest. And let me tell you, there is no loot whatsoever to speak of in the forest itself, which makes me think that her den might be a mini dungeon that you can enter, like the entrance to The Sunken Caverns. If that is the case, then then entrance should be in the exact middle of one of the Deep Forest tiles; aka [-200,400], [-100,400], [0,400], [100,400] for the 4 top areas, or [-200,300], [-100,300], [0,300] for the 3 lower areas.
However, if I'm just completely wrong, and the Den is not actually a cave entrance or some such, then I have found at least one instance of ruins in the Deep Forest that has the inside area of 8x8 tiles, possibly matching the "8 meters deep" part of the description.
That's where I'll leave my investigation for now.
Acacia's den is in that one deep forest tile on the east side, at least that's where I found it at a few updates ago. It's just a small cave with a campfire for light and a pile of leaves for Acacia to sleep on. It's not even a separate interior you have to load into like the dungeons. She'll sleep there all day then start roaming the deep forest tiles at night.
Oh? Interesting. I was sure that the devs would have hid it in one of the two backmost Deep Forest areas to make it as difficult as possible to reach. Although perhaps they are aware of just how frustratingly tedious the area is to traverse so they decided to throw at least a little bit of a bone our way. I will go there to explore myself for sure, thanks!
