So it looks like these groups do not terminate "MIA" members:
Alpha Chi Omega
AST
Kappa Delta
Kappa
TriDelta
Theta
Pi Phi

I guessed the affiliations from either username or signatures.

So, OP, we are interested in hearing something that makes a little bit more sense...

Add Phi Mu to the list. We don't terminate the missing sis either -- but we are very glad if and when she's found again. :)

and Theta Phi.

Gamma Phi Beta doesn't either.

However, in instances where a member leaves with a large outstanding chapter bill, she is not considered to be in good standing, and efforts are made to collect what is owed. When I read the OP's post, the first thought that came to mind was that she may still owe money to the chapter, and her IH is trying to collect.

And Delta Gamma

I know it sucks you can't have greek life, but personally I don't think you should WANT to join another organization. You join yours for a reason...because it's where you belong. Those are YOUR letters now. IMO I wouldn't ever want any other letters

Suspension only occurs if there is cause.

Otherwise, in Alpha Gam, you're a lost sister if you disappear.

So, there's another.

We rip those letters away ASAP...you'd better get that update back quick! JJ...add AOII to the list of groups that don't drop sisters just for being off the radar. I agree that she probably left in bad standing.

So the list is now

AOII
DG
AGD
Theta Phi
Phi Mu
Alpha Chi
KD
KKG
AST
Theta
Pi Phi
Tri Delta
Gamma Phi

13! I hate typing on my phone!

Add Alpha Xi Delta to the list ... sisters are just listed as lost.

waiting on
ZTA
ASA
AEPhi
SDT
Phi Sigma
Tri Sigma
DZ
SK
Alpha Phi
ADPi
DPhiE
ChiO

Wonder which one the OP is a member of? This has the potential to go off the rails, does it not? (cue hopeful tone of voice; it's been too long since there's been a good wreck). Realistically, on second thought ... then again, not going to say it. Practicing restraint (although it's killing me).

(To any of the NPHC ladies or MCGC ladies reading, the OP said she was in an NPC group; if your group does not terminate members who have gone MIA, and you want to be added to the list, you are more than welcome. Lots of place settings at my table!).

I'm pretty sure Chi O doesn't either
(though 1 exception might be if they are not in good financial standing ...
i.e. left without paying for initiation fees or their pin!)

ZTA does not terminate lost sisters.

DZ does not either. Most of my pledge class is "lost" but none have been terminated.