Either she is trying to sneak up on Carmilla or the former buried her there....chances are Carmilla buried her probably....though considering the fact that their relationship with each other is literally
"Wants to kill the other"
Yeah it's not that weird for her do to that
No wonder we didn't have Elizabeth's presence in the summer event an event that she would have loved to participate in
Perhaps it got removed because said tag meant for her Caster / Halloween version. Because Elizabeth debuted in Fate/Extra CCC, she's tagged as lancer_(fate/extra_ccc) for her original / lancer version.