Mom's can be the sweetest girls with no litter, but give her space and caution when she is nursing. Some of my best moms really don't like their pups handled or intruded upon.

As to the bad first litter, always best to give her a second try. Some females just don't know what to do with the rush of hormones.

As to the chewing and trying to get out, after the first litter females tend to calm down a lot. I give my girls a long break in a nice vacation cage, they get a wheel and the companionship of many other females. I spoil my rats I know, but they are awesome moms and give me great plump feeders.