I agree, these kittens should not be in the shed, and the less time you spend with them at this stage in their lives, the more difficult it will be to socialise them in the future. If you do not have room in your house and your other young cat cannot adjust to them, then you really need to put them up for rehoming or get them to someone with experience of young kittens. Your older cat may simply be one of the many who just don't get on with other cats, and would far rather be on her own. This is certainly the message that's she's trying to give you right now.
If you do decide to persevere with this, the advice in the following links may help you.
http://www.catchat.org/hierarchies.html" onclick="window.open(this.href);return false;
http://www.catchat.org/bonding.html" onclick="window.open(this.href);return false;
http://www.catchat.org/cat_aggression.html" onclick="window.open(this.href);return false;