Wow...many things come to mind initially about how this should have and could have been prevented and many other things that you are probably coming to realize now, but it's a bit too late for that now...
....so, most importantly, at this point you need to realize that the condition with your girl being prego, by a larger male, and being very small is that she IS at great risk with these 3 factors alone. Add to that your inexperience and you have a very serious siutation on your hands.
At this point I would suggest that you do
whatever it takes to find an experienced breeder nearby who would be willing to help you out--one who will be likely to pick up and take note of danger signs more than the untrained eye. Have an x-ray/ultrasound done closer to her due date (around 50 days). This will give your vet a good indication if the pups appear to be too big to deliver naturally, or if a c-section is expected to be needed. If your vet is not well seasoned with this type of situation, find one who is. Find an emergency vet, have their number on hand and let them know in advance of your situation and that you may call on their services. Get the supplies you will need for her whelp ready now. Plan to be at home with her closer to her due date and do what you can to educate yourself on care for newborn puppies. You need to be aware of what some of the signs for health problems in young pups are--if you encounter one, you will have little time to act!
And most importantly, in the best interest of your female...have your girl spayed as that is the only foolproof way to ensure that her life will not be put at risk again...other options don't seem to have worked.
Good luck!