I know I've said it a million times and I hate to sound like a broken record, but I would really suggest reading
I Heart Recruitment by Coffey and Gendron. It's fantastic.
Do you have pre-recruitment workshops? Ask your chapter (collectively) what they are looking for in new members. Then, for each quality you are seeking, brainstorm questions you could ask potential members to see if they have those qualities.
Also, ask your chapter why you like being XYZs. For each quality you like about XYZ, think what you can say to portray that to potential members. And be specific. Instead of merely listing qualities to potential members, give specific "evidence" of those qualities through events, awards, achievements of members, etc.
I'm assuming that you are in an NPC sorority. Use the national sorority to your advantage! Do you have a consultant visiting you during pre-recruitment week? If not, you should request one because she should be able to help you out. Also, do you have another chapter of your sorority nearby? If so, invite members of their chapter to practice recruitment conversation with your chapter (and maybe even a sisterhood event afterwards).
I'm going to assume that your chapter does do informal recruitment/COB in addition to formal recruitment. It's ok that your chapter doesn't fill total through formal recruitment. Your chapter likely fills a valuable niche among Panhellenic sororities and you just need to be able to look in other places for potential members. Instead of COB "events", it may be best to recruit on an individual level. Your members have friends/acquaintances outside of the sorority. Encourage members to meet and befriend women in their classes, other activities, friends they know on their floor/hall/dorm, etc. and do "normal friend things" with them. Maybe bring another sister along. Once she is friends with several of your members just by doing "normal friend things", and if you and other sisters would like her to become a member, talk to her about joining.