The good times aren't over yet!!! My suggestion is to get involved with a local alumnae chapter as soon as you graduate. It won't be exactly the same as your college events, but alumnae events are tons of fun, too.
For example, all of the young alums in my area meet for Happy Hours, movie nights, and weekend brunches on a regular basis. We also are very active in assisting the nearby collegiate chapter, which keeps us in touch with our college days to some extent.
Grab some of your other graduating sisters and take them to the next alumnae chapter meeting in your area to see what the chapter has to offer. Having a few of your chapter sisters with you will help to "break the ice" when meeting other alumnae. You'll have fun - I guarantee it!
And as for worrying about letters on your car and whether or not you'll wear your mixer shirts again... Keep those letters and show them off with pride! I've still got a DZ sticker on my car, and I'm looking for a DZ Alumnae sticker to add to it.
Also, since we have casual Fridays at my office, I still wear my social shirts regularly. In fact, I don't think that there are many shirts in my wardrobe that don't have Delta Zeta on them in one place or another -- and I'm 27 years old!
Always remember... you joined ZTA for a lifetime, not just a college term. It's up to you to keep your love for the sorority strong -- and alumnae chapters can be a huge help with that.
Good luck and congrats on your upcoming graduation!