Karla is absolutely right. Have the Vet check that nail as you don't want it to get infected and, while there, ask them to clip the nails for you as they are WAY to long! Check under the hair on the sides of all her feet and she if she has dew claws. She should not have them on the back but she may. The dew claws also have nails and, if not kept trimmed, can grow around and back into the foot pad.
I usually use a Dremel on nails but you have to keep that long hair out of the way or it will get tangled in it. May take a while for the dog to get used to it. If you don't have Styptic powder or sticks, you can use Corn Starch or Flour in a pinch.
You should make a Vet appt before there is an infection, let them do the nails, ask if you can watch, then stay on a regular nail maintenance schedule. The longer the nail grows, the longer the quick (vein) inside the nail grows.
You need to get her to the Vet or groomer & have ALL these nails trimmed......They are way too long & are at high risk of a tear because of length.....She will have trouble walking before long.....Nails are prone to infection for obvious reasons......I'd have the Vet do it! Karla