Hello Emerion. Welcome to the forum.
You could try and hand darn the tear. There's nothing to lose by trying. If it's a busy pattern it'll work better than if it's plain or light coloured.
It'd be a pity to shorten the skirt if you like it the length it is, so I wonder if it would be possible to seam the tear out? If it's a full skirt with lots of fabric in it, you could run a straight seam from just under the waist down through the hem, losing the damaged bit. If it looks odd, depending on where it's positioned, you could then make a second seam but without taking such a large chunk of fabric out, to match it up better.
Can't you get ballpoint or stretch needles for vintage machines? I use a straight stitch when I stitch jersey.
Sandra.
xxx