BIDS
 

I went through formal recruitment and got into the house that I wanted. Unfortunately the night of pref I also got an email for an externship opportunity. I choose the externship but missed all the girls from the house. If I wanted to pledge this semester, how would I go about doing so?

You ask the members of this chapter what your options are instead of consulting strangers on the internet who know nothing of your situation.

I'd contact their membership chair and tell her that you are still interested. Ask if they are still open for new members.