I know this is a little late, but that hair fixable. First, i'll explain a couple of things so you know a little why is the hair frizzy
In G4 they used Polypropylene for the hair and tail (mainly on the tail), polypropylene is a very cheap hair fiber wich disintegrates in 20-30 years but sometimes even less. Poly is such a bad fiber that it can get very tangled and VERY frizzy just by brushing it, even if it's new in box. In early G4 (2010) they suposelly used on nylon on both hair and tail, i have a post contradicting it tho because one of my pinkie pies hair disintegrated meaning that they mixed polypropylene with nylon:
https://www.mlptp.net/index.php?threads/g4-hair-disintegrating.120732/ So the tail is that bad because it is Polypropylene, and probably the mane is mixed too, So in some years they will break and turn into dust.
You can do various things to make it better, you can use some shampoo and conditioner to make it softer, a boilwash (dunking the hair in hot water and combing it) but those things are not going to make a difference with the tail. The best method for it it's to flat iron it (you can use a curling iron too), it's what i do and the only method that works for me with the tails. Here's a tutorial:
You can also rehair her, but putting new hair is VERY difficult in G4 ponies, because their head don't pop out and you get to the inside like G1s, G2s and G3s. They have a part you have to cut with an x-acto knife to get to the tail, and glue it back when you're done. I stopped collecting G4s because of how difficult they are to manage in that way and how dissapointing the quality is.
