Ok, I've had some picky buggers and I also feed LGRS- so here is my 2 cents hehe.... Try a plop of some cottage cheese! Mine don't like it, but I know Ed feeds his gliders at LGRS some once or twice a week. If they like any kind of yogurt, I'd go with Greek yogurt as opposed to Yoplait or anything else because it's higher in protein. JazzNZoeysMom mentioned ground turkey-> drives mine crazy, too. Kyro mentioned an omelet- I've made a few omelets for my fuzzers containing whatever veggies I had in the house, tossed in with the egg (Ed also says using just about any kind of cheese in an omelet is OK as well- I used Mozzarella).
Right or wrong, I give an extra source of protein MOST nights, but there are some nights I offer the protein and no LGRS, and some nights the LGRS and no extra protein source. And there are the special occasions when those little furballs are being particularly picky about their food and I mix it ALL in ONE bowl together! And I mean EVERYTHING! Get a fork, and smush the frozen LGRS into the extra protein source (egg, burger, whatever), puree/dice/whatever the fruit into there->all of it mushed together. This way, "I" know if they are eating, they are eating what they NEED, not what they decide to pick and choose about.
Someone correct me if I'm wrong, but I don't believe mealies contain much protein. They are more of a treat rather than something for nutritional value. I don't know about crickets on that one, though.
Bottom line-> don't fret! If you know what they like, feed it to them. Give them something new from time to time, because like children, one day they will like it but the next it will be a big fat NO. My leu Penelope is about the age of yours and she hasn't had a mealy yet, and she will not TOUCH a freeze dried cricket. Actually, I have yet to find a treat of any sort that little girl will eat... but that's besides the point. Just know you are doing the best you can, mix it up so food doesn't get boring for them, and everything will be fine. The most important thing to remember with sugar glider diet is: all things in moderation! Variety and Moderation. You're doing great! :)