My 13yo want to date 16yo

So I have a 13yo daughter, she has been seing this boy, he is 16yo....no matter what we do, she stil see him....this have caused alot of headache for me and I realy dont know what to do...she is a princess and he is a bum...but ok, I have respect for her feelings even thou she is 13..feelings is feelings....
We live in a strickt catolic area with valeus from the old church...
what to do???
do I let them date?????
do I kill him and dont let her go out until she is 18 or what?
I have started to accept that they are dating, in my mind not official.....
is it better to let them see eachother nonofficial and let her see and make her mistake for herself????
please help.
then i have a 16yo that is dating, she is doing great and i have not worries...
the thing that is disturbing is she is 13 and not 15-16----
thankfull for advice....
also she looks like she is 18 and have a body like 18....but she is fucking 13 13.....