Cat behavior/scratching question

Question
Hi, I'm hoping you can help me with an issue I'm having with one of my two cats.  A little background on both of them... We have two, a male and a female, both fixed, and adopted from the humane society at the same time. The male is approximately 1 year old and has become the dominant cat of the two, the female however is 2.5 years old and is mostly reclusive.  They are both 100% indoor cats.

The majority of the problems we've had have all been with the female.  I know when we adopted her that she had spent the better part of three months in a small animal shelter cage and was horribly sick with kennel cough and diarrhea.  We nursed her back to health and she started to get attached little by little to us, as she adjusted to us, we adjusted to her.  She has become very scratching oriented lately.  She's had this problem since we adopted her, but it's become noticeably worse.  Her normal behavior is to scratch anything she can get her claws into (aquarium stands, night stands, furniture, carpets, wood door frames, and even glass table tops!) until my wife or I correct her (usually with a firm NO and/or a squirt from a squirt bottle).  She'll stop, quite literally watch us until we're not looking anymore, and continue to dig.  We asked our vet about it and his reply was simply: "Maybe that's just her thing..."

I'm at a loss, this has turned into the battle of wills between this cat and I.  After not getting more than two hours sleep for the 10th day in a row, she's winning.  Her favorite hobby lately has been to come into the bedroom and claw the edge of the bed or the corner of the nightstand next to my head while wailing like she's on fire.  When I stir she runs away and comes back ten minutes later and continues to dig some more... She will repeat this process until my wife and I are totally awake around 3:30AM.  We've tried the scratching posts (she ignores them, digs at the bookcase two feet away from the post even after putting her on the post and praising) & the tape stuff (she will scratch at it until it peels then try to eat the peeled edge), the nail caps (she chewed them off in 20 minutes), and we keep her nails trimmed.  She gets VERY violent (squirms, scratches, bites, hisses...) when having her nails cut so we wind up wrapping her in a towel to clip her nails. (I've often wondered if there isn't something physically wrong with her nails because they don't cut cleanly like the males do, hers shatter when they are clipped.  The layers of claw just come apart almost all the way back to the root of the nail.)

Also, is there a chance she's scratching and digging for attention or to just be simply  defiant?  She seems like she knows it's a bad behavior because she usually runs away if you look at her while she's scratching, but lately she'll just stop scratching, sit there with her claws embedded in something, and try to stare me down.  She's become immune to squirt guns or verbal commands.  The only thing that stops her lately is physically removing her and carrying her to a scratching post. (if you can catch her before she runs away!)  

I refuse to give up on this cat, but I am at a total loss as to what can help at this point other than declawing the cat.  She's already been taken by a family to the shelter once, that's not going to happen to her again, but I am not adverse to declawing her as a last resort since she is, and will always be, an indoor house cat.

Thank you in advance for you help!  It's more appreciated than you might know.  

Answer
Cats scratch to sharpen their claws but also to mark their territory.  She may be seeking your attention or may have an obessive compulsive disorder for which she needs anti-anxiety medication.

What I would recommend is gettting FELIWAY and spray it where you don't want her to scratch, try adding lemon juice to the water to see if that helps in discipline, booby trap areas with balloon in the hopes that her claws popping the balloons will scare her to not scratch, wrap areas with aluminum foil, baiting the scratching posts with cat nip and treats and then when she is using them PRAISE her and give her a SPECIAL treat like tuna or chicken breast....also make sure you have SISAL rope posts, not carpet and consider getting an old tree stump for scratching as cats often like the feel of bark on their feet.