Hi Jaymie,
It's just been a few weeks since you lost Crystal, you're thinking about her constantly. It's not surprising that you might mean to call Luna and say Crystal.
When I first got Kali, I told myself that I wouldn't compare her to Qorqui, or expect her to be "like" Qorqui. But I found that wasn't so easy since my loss was still pretty new at the time. So when Kali would do something I couldn't help thinking "that's not how Qorqui would have done that", and it kinda got in the way of my ability to appreciate Kali as her own individual.
I've since gotten past my problem of comparing Kali to Qorqui and now appreciate Kali as Kali. When I changed my attitude, she came around too and (like Qorqui) is one of the most attentive and affectionate little critters I've ever met. (She's still won't eat dry food without fresh pressed apple juice or a little Prego soup mixed in though.

)
Don't try to get Crystal out of your head. You need to go through the grieving process. If you supress it, you're just asking for other problems later. Just try to remember that Luna is not Crystal, but she is also special very in her own way. She WILL to things differeently than Crystal did, but that's okay. She's Luna, she's a different kitty. Give it time and the bond will form. But don't try to rush yourself in getting over the loss of Crystal. Let that happen in its own time. I think then you will find that it's easier to accept Luna as your new special friend while still keeping Crystal in her special place in your heart.
Tim