I agree with franknbeans, not a big fan of vet wrap myself (my horses really aren't either). And they NEED their tails in the summer.
I personally swear by my method of braiding every winter, all winter long. I find the time when they wreck their tail most is in the winter (from mud, wet, etc). I also use a detangler every time I brush them. I normally use showsheen since it's pretty cheap when buying in bulk and you need very little of it. I also swear by the Oster mane & tail brush. Buy one if you don't already use one. They are super effective in getting rid of tangles and pull out very little hair, if any. I also don't wash unless absolutely necessary. I find shampoo strips the hairs of their natural oils and makes them more brittle, causing more breakage. I only wash before a show or major event, or if their tails are exceptionally dirty in the winter. All three of my horses have beautiful, thick tails. One of them had a pretty average tail when we got her, quite broken at the ends and thinning. After a while with me her tail is now one of the first things people comment about her and it's only getting thicker. I can hardly wrap my hand around it it's so thick and, after leaving it in a braid for this last winter, I literally had to take 6 inches off and it still touched the ground. I've also never used a growth product, except fresh ground flax seeds which are high in omega-3's and help hair quality.
These are just some of my opinions. Good luck with your mare, I think time will make all the difference! (And sorry for my long post, I like to talk!)
I also attached some before and after pics since you asked for some (they're the best I could crop up from what I have).