Lulabelle is probably just scared, it's a new home, new situation. What i've done with mine to avoid any biting what so ever is just out right pick them up. Don't poke around, and definatly don't put your fingers near their mouth of course. Building trust by picking them up firstly, then let them crawl around on you, or perhaps even your bed if you can put them on your bed, and keep a close eye on them. Then, after holding them, give them a treat and put them back. When they bite, Make a loud "ouch" sound or something, so they know they hurt you. They don't want to hurt you, rats aren't aggressive in nature. :3 If it makes you more comfortable, put on gloves (Not plastic ones) when holding them at first, but be very gentle! That's what I do at the pet shop when risking a potential biter of any animal. Even the animals we sell there, I tend to bond with so that they're a little nicer when going to their forever homes.
Make sure you don't smell like food when holding them too. That's about the only time i've ever been bitten by mine, but I learned quickly on that lol.
If you put them in the bathroom to do that, make sure they can't get into any air fresheners, and if you have an auto-freshener that plugs in or sprays so often, take it out. That is bad for them.
In general too, if they ever get out in your room, they're pretty easy to catch. When my husband and I first got rats, our cage door was faulty and they escaped. Good thing our door was closed. Problem was all the hiding spots. But we found them and after an hour of searching lol.
Good luck on the new ratties! Just remember never give up! Where there's a will, there's a way. Rats are so great and the reward of having them as your pals is one of the best things ever.