Hattie -- It's a really cute nn yet I don't like it enough as a stand alone while I intensely dislike
Harriet. It's the same problem I have with
Hallie which I adore (not enough as a fn for me but I hate the full name).
Hattie May is sweet but too simple and it lacks sophistication -- especially since
Hattie is a nn. Now
Hattie Matilda has some spunk! I do like the flow of that one.
Lucy -- I love
Lucy! My fave
Lucy combo is either
Lucy Eleanor or
Lucy Marigold so as you can see, I've given some thought to this name!
Re: your combos, I like
Lucy Margaret best.
Mabel is NMS, mainly because it has a really dated feel to it, imo. I also don't enjoy the sound although I understand why people would find it attractive.
Mabel Catherine is really nice.