If the girls are older (as in this case), they are usually fine. But you have to do slow intros, regardless. Start buy using fleece blankets that you can swap out, then swap out pouches (you should always have two pouches in each cage, even w/single gliders), so they can start getting used to each other scent. Do that for few weeks, then actually switch cages, let them spend a few nights in the others cage, then switch them back. Then start taking them both out in zippered bonding bags (which you should be doing individually with them already every day), so they can smell each other through the pouches (they will probably crab.....just let them do it.) Then after doing this for about a week, take them into a tent, or shower stall and let one out. Let them crawl on the other one, sniff it, etc. After a while, put that one back in his pouch, and let the other out. Do this every day for at least a week, then try letting them out together (keep a big piece of fleece in case you have to seperate them quickly.) Do not let them ball up. Also, do not let them go into a pouch together for a while, so you know they are getting along. Sometimes it is love at first sight, other times, it takes a while (sometimes QUITE A WHILE! lol) But don't give up unless they just fight every time.....then it is most likely they just don't like each other and that won't change, but give them time, sometimes they just have to work things out. It isn't easy, but is rewarding when they get together! Good luck!