Our presidents used to pull this. They'd hold emergency meetings and tell us we had to get so many girls. Well we got enough girls and many of them(sorry to be mean-- were white trash). I'll explain one girl in a minute. Then some girls depledged others decided that college wasn't for them etc. So then we lose members. This summer we have lost four counting me.
I would suggest not worrying so much about losing your charter. Work hard, but chances are you won't lose your chapter unless you have 10 girls or something total in the house.
So there was this one girl we had join our house. At our retreat we reveal stuff and she told us how she used to be on crack and had to go to Narcotics annoymous. Okay-made mistakes move on. anyway her cousin joined our house(4.0 GPA), but they both did pot all the time, they talked back to our advisor!!!, they wouldn't come to mandatory stuff. Anyway fast forward to last week of school--- the one girl(#1 who dropped out) calls me and says," you should be lucky it's the last week of school otherwise I'd kick your ass. Stop talking crap about me." I asked her who said I was saying stuff and she replies," Don't talk to me " and hangs up. Well I was one of the only sisters who was nice to them when they first joined. Other peole talked more stuff then I did turns out they saw my name on a letter that was turned into standards(we had 7 or more of us complain to standards about them, but these girls only saw my name)
So believe me numbers do not make a house.