How do I shape my shelties long stringy tail hair?

You can trim the long hair to make her tail more even. Use thinning shears -- NOT straight shears, trimming just a bit at a time.

Put her on a stable surface such as a grooming table or a place where she'll stand still for you. Hold her tail out straight behind her with one hand, and with the other carefully snip at the long ends with the thinning shears. Don't take a lot off at once, remember you can't put it back once it's off but you can always cut more. After your first cut, put the tail down, brush it, lift it up again and look. Repeat this until it looks even.

Post some pics when you're done! Happy trimming!

 

Not to worry, as Hanne said the good thing about hair is that it will grow back, and maybe it will come in even! If you do it again, try to shape it a bit more, taking less closer to the body so it's not so much a straight line. Still, it doesn't look bad and in a few months it will look fine.

I didn't ask you how old she is. If she's between one and two years old, she's probably having her first coat blow and that may be why she looks sparser. Puppy coats are alway full and fluffy. Her new adult coat will grow in a bit coarser.

Your pup is still really cute and I bet that tail still wags!