My collie seems to have developed a VERY annoying habit....

She's 5 months old and we are trying to teach her not to jump up.
This past week or so she has started not only jumping but biting with it!!!!!!!!!
Not a proper bite, more like mouthing but you feel it and as soon as she gets down you feel the teeth going with her.
She has already put holes in some of my favourite dresses!

Why is she doing this????
She barely bit at all as a puppy.
She's a lot bigger now and she doesn't seem to get not jumping.

When she jumps we ignore her, turn around and praise when she's down.
Two or more weeks consistently and there's been no improvement.
Sometimes I wonder if she's actually a collie!
for an intelligent breed she's real slow to pick up some things.

When will it stop?!?!?!

Maybe try treating her along with her praise? Some dogs are more food oriented and think praise is just lame.

You can use a clicker too, if you think it will help. I personally find them annoying, but I have heard many good things about them.

Given enough time, and if you're consistent enough.. your dog should learn. Also, just because your dog is an intelligent breed, doesn't mean your dog is smart.

Maybe I will try that.
I have heard great things about clickers but I don't use one because as you say, I find the noise extremely irritating.

She's smart with some things, a lot of her commands like sitting, waiting, leave it, crying on command etc etc she learned in a day or two but others it just never sinks in!
She's 5 months old and only now is she starting to walk nicely on lead!

Have you tried having a toy with you, so when she think about jumping up or mouthing throw her the toy if she brings it to you ask her to sit & treat. Good luck.

No, but I will try that!

My puppy is 5 months old too! He's a smart Lab crossed Great Pyrenees doggy. Sometimes he seems so DUMB, but the more stubborn they are, the smarter they usually are!

Dillon is still doing this behaviour sometimes at 18 months.
Especially when we return home or are getting ready for a walk or on a walk its mostly excitement and them not knowing how to channel it.
We have taught get a toy most times he does sometimes we need to fetch the toy to redirect him but 8 times out of 10 he does get it and sometimes he doesn't need telling.
Consistency is the key.
On a walk we take a tug toy and redirect him.

At that age they aren't dumb for not picking things up just have so many other more important things to do and think about. I can see Betty thinking about what do do next rather than concentrate on doing what I say. It takes a bit of concentration for them to learn to control their impulses I think.

My Jack is the cleverest dog I've ever had but, at 18 months he still jumps up and pulls on the lead yet in only his second ever agility run he beat 175 dogs to take a trophy for 3rd place! I think with these intelligent collies, they are able to work out whether it is worth it to do as you ask!

Jack is rather lovely you must be proud !