as far as the constipation is concerned i have a baby boa who has the same problem he doesn't poo for a couple of weeks, some say its normal for some babies.As far as feeding mine does eat unlike yours you should try soaking the food oblect in warm chicken broth the heightened smell should intise her.

what're her temps and what's her cage setup like?  this sounds like a little more than just infrequent poos.

From your description, my first thought would be that she is dehydrated. I would soak her for about 20 minutes/day and see the vet this weekend.

+1 for dehydrated. I'd put a shoebox in her enclosure with a few inches of water and let her soak for several hours at a time each day until you can get her to the vet. FYI, once they look sick, they're usually quite sick and waiting several days for the vet appt can be the difference between life and death.

+10 gfx

Ok, I am going to soak her as suggested, and I have a vet apt tomorrow for my gecko, so I will call ahead of time and see if I can bring her along too. If not, I will just make another apt. 

I offered her a large mouse pinkie earlier today, and she ate it! So- hopefully she is on the way back to feeling better, though a vet trip is happening soon. 

plus 1 for dehydrated.

Boas have a slow metabolism.  They need water to digest their meals.  Soaking is good to help, but short soaks can lead to further dehydration.  Make sure the temps and humidity levels are correct in the enclosure (78 - 82 ambient temp, 88-92 hot spot 50-60% humidity).  Mist the enclosure to ensure the humidity is correct or a little higher than necessary to assist with digestion.  Once those perameters are met try offering a smaller meal.

Check out this link for more info on caring for your boa.

http://care.redtailboas.com/Ultimate_Care_Guides.html

I hope everything turns out OK for the little one.

UPDATE: We spent some time hydrating her, and she is now eating again. Her responses are much higher, and overall she seems much better. 

After speaking with a vet, she also suggested hydrating her more than we are now. 

Her temps are at a perfect 90 for her hot spot, and the rest of her tub is anywhere from 79-82/83 depending on how warm it is in the apartment. The rack we have is made of melamine, and does not hold humidity as well as we hoped it would, so we spritz everyone daily. The average humidity is about 52%- but we have began using a fogger to up the humidity for her, as well as the others to prevent further dehydration.