Can a friend unblock you just to see whats on your timeline then block you again on Facebook?

[504Lady]

I wasn't able to messege her until this morn I clicked on chat box messeges and I noticed her name in blue for the first time,like it was gonna allow me to send her a messge I started to but didn;t,I then waited and checked again and her name went to Facebook user in black ink again,Go figure!!! Is She Snooping in and out on me to see my timeline post??? Last week I discoverd my facebook friend vanished.I don't see her comments,likes,timeline and I can't search for her anywheres.She has a lot of the same mutual friends I have and when i had to go on another friends fb profile whom is not friends with her and there I found her and able to search her.She has the same fb and same mutual friends,but me.When you BLOCK a friend Can they UNBLOCK and BLOCK again? Otherwise I can't not see her anywheres except that one time on messge this morn for a few min. very strange! Thanks for any Help.