CM,
Calm down, your emotional state is not going to help her at all.
Be calm and reassuring, If you need to take her back to the vet to have him help you administer the meds if you are unable to emotionally handle it. Make sure she keeps hydrated with the ringers, this is the most important.
Try to give her the pills in a small treat, something she will definately like.
If that wont work get the pills alone into her throat and gently hold her mouth shut until she swallows.
What is going on is the parvo causes her intestinal tract and stomach linings to become irritated and inflamed. worst case it sloughs off and is vomited or crapped out, this is when it is serious and usually fatal.
She may not feel like eating at all and you will have to bear with her.
you need to let her stomach and intestines rest, get her hydrated and medicated and then start her on a bland diet after a few days, rice is the best for this.
Your vet is the best coach for this and is a phone call away. Most vets will be understanding and give you pointers over the phone.
Make sure you use bleach, natures miracle orange oxy power (w/ enzymes) or whatever your vet recommends on the areas where she has defacated or vomited to prevent spreading it around. If you can throw it out, bleach the heck out of it and throw it away. if you can burn it, do so.
You both are going to go thru the worst week or two of your lives. There is no easy fix to this. If you think you feel bad imagine how mary feels. keep yourself calm, stressing mary out can worsen her condition. Do not make any rash decisions.
What i'm telling you here is coming from my own personal experience with this and from the merck/merial manual for pet health.
There is a myriad of info availbale to you online. but your vet is the best option.
http://www.cpvh.com/Articles/39.html
http://www.workingdogs.com/parvofaq.htm
http://en.wikipedia.org/wiki/Canine_parvovirus#Treatment