I realise this probably comes up A LOT (I know it does on other games forums) but if anyone can help me I would really appreciate it.

I'm looking to make a combination melee combat / caster character - someone who can finish simple fights just using a weapon but has useful spells to call on for harder fights. I want a caster in the party because magic makes a huge difference, especially at higher levels, but I get annoyed with caster henchmen because I find they will waste their spells on randoms, so I either spend a ridiculous amount of time resting or don't have the extra fire power in a fight that actually needs it. So I want to be the caster but I also want to be able to contribute to those fights that don't need magic.

I'd like to dual-wield ideally, and a bit of a nature theme would be a bonus. I'd like her to be a half-elf too. Other than that I'm not fussy.

Importantly: I don't mind if my choice makes the game more difficult.

I actually enjoy RPGs more when the combat is challenging, when I have to make good use of all my options and pause frequently to reassess the situation. I'd much rather play a character who is difficult but enjoyable than an optimal build which makes things easy. And if I'm really struggling I can always turn the difficulty down.

I think my best options are cleric, ranger or ranger/cleric, with multi-class possibly being the best choice, but it seems to have heavy drawbacks to me (especially being unable to reach the higher levels of either class).

(BTW just in case it's helpful I did play the game back when it first came out, and finished it as a cleric. I just picked it up again since it was free and I'm realising just how much I didn't understand the first time around.)

They two magic/combat hybrids are cleric and druid.

Clerics in D&D are the most overpowered class, including neverwinter nights.
They can run around in full plate armor casting magic with shield.

Like wise Druids can cast while wearing armor as well and have buffs and good spells.
You get a pet ... bear is typically the brute you will want. You can buff up the pet and it becomes really powerful. The biggest down side of neverwinter nights druid from pen and paper would be not all spells were implemented.

Pretty much same problem with all druids ever done in D&D games.

So you want to play a melee character that can cast spells and stuff to make him fight better? Paladin, Champion of Torm, and Cleric would all fit that description. Especially Paladin and Champion of Torm.

Paladins are exactly that... they are a melee class that casts spells to enchant their sword and improve their melee combat abilities. So you could just go pure Paladin. You could also add some Champion of Torm to that too if you want, or just go pure Paladin.

Clerics can cast spells AND fight in melee combat, but Clerics focus more on spellcasting than a Paladin does.

Druids are my favorite class. With their powerful defense spells they make excellent fighters while also possessing powerful offensive spells. They are not as versatile as mages or clerics but fill any role (fighter, mage, healer) successfully.

A little bit tricky but rogues are also an option. With high dexterity they can dual wield without a problem and with high UMD skill they can use most spells in the game. You also get to open locks, disable traps and lay powerful traps so what more can you want? I remember I finished off some of the most powerful bosses in the game with traps without touching them. It is kinda harder to finish the game with rogue than Druid (which is very easy) but it does the job.

From what you have said, I think Cleric or Bard are excellent choices. Both can melee and are backed up with spells.

A build I frequently use which covers all the bases and sounds like it may be for you is this one. It really is a powerhouse and very self-sufficient.

Monk with ranger multiclass. Enjoy.

I second the Cleric suggestions. If you want to be in melee and cast spells, that's really your best option. Paladin also works, though their spellcasting starts at level 4 and they have a bit of a different spell selection than Clerics. Druids are also a viable option, with bear for tanking, wolf for knockdown (I think), or panther for sneak attacks. Bards can be viable melee casters as well since they can cast in Light Armor, but they take a bit more finesse to work with.

I'll also note that rangers can cast spells at level 4 just like Paladins, and do well dual wielding if that's the route you want to go. They get those feats for free.

EDIT: If I had to give a top recommendation, I'd go with a pure cleric, and take a look at Bless, Divine Favor, Magic Vestments, Magic Weapon/Greater Magic Weapon spells. You can also dip two levels of Fighter for feats and not hurt too badly for spells as long as you don't mind your DCs being lower than they should be and getting higher spell levels later.

I say you go Sorcerer/RDD with a dash of paladin. You get a nice boost to your stats and the three classes share synergy around the Charisma ability.