[Mel]

1) I think you have to kill Adalon before she teleports you out. But you shouldn't kill her anyway unless you're evil.
2) How to kill a dragon:
Be very careful and have loads of healing on hand. Use plenty of ranged weapons if you're fairly low level, if you can afford them arrows of dispelling work well. Cast the mage spell lower resistance (or something like that) on the dragon before the fight starts (more than once if possible, I like to start the fight with two mages casting this simultaneously then both of the casting it again later in the fight). Cast haste, chant, resist fear and any other protective spells you can think of on your party BEFORE the battle. Melf's minute meteors is a great spell for your mages to use during the fight.
Two of the dragons found in the game start off a s nuetral characters and won't attack until you attack them. This gives you a chance to cast protective spells before the fight. it also gives you a head start with offensive spells since the dragon won't go hostile until the spell hits them.
Above all, I wish you good luck.