I love Bernadette. (She has a LOT in common with my wife.) The one weakness in her writing is that you never get a sense of why she loves Howard.
Amy is desperate, but she’s also so well-written that you can buy that Sheldon is exactly the guy she would fall in love with. Leonard is so desperate to please and that’s what Penny needs: someone who is good to her. But why does Bernadette love Howard? She dislikes so many of the things that make Howard Howard: that he’s a Mama’s boy, that he’s an uber-geek. She doesn’t even particularly like his space program stuff.
In one episode they address this. She has a love/hate relationship with her mother also. Thus the bond with Howard.