My Mac Mini crashed so I can't test for you. But I was connecting to my Mac Mini with my Mac Air without problems until then. However, even though I have an account for both my wife and I, I did not have her iCloud setup on the Mac. Also, I do not have a Time Capsule. My Router comes from Verizon FIOS I assume BTMM setup up the router properly (maybe uPnP or something) because I did not touch the router.
I would test your setup within the local network first to make sure it works properly. I read that you can both be logged into your Mac remotely and locally at the same which was a surprise to me.Yes I am unaware of this, how do I do this?
1. You did not say if you setup the iCloud Setting on your Mac Mini for your login id. /Settings/iCloud/Back to my Mac
Yes I set the log in credentials as both my wife and I under BTMM on the Mini
2. Under /Settings/Sharing/Screen Sharing On (I also have File Sharing on)
Yes I always have Screen Sharing on for using the Mini while others are watching TV.
3. If it still does not work, I would just make sure you are logged in and try again. Maybe log her out.
I was hoping that by letting me put my iCloud username and password under BTMM in iCloud settings that I wouldn't have to sign her off iCloud and me in. But I will try with me signed in to iCloud on the Mini.
Thats all I got. Good Luck.