ive tried to DB and what i did was log onto her account(when shes not playing)on her pc then log into mine on my pc
First: Don't do Accountsharing - Its Witchcraft.

im doing the regular quests i would do if i was soloing and yes it goes faster but i dont seem to be lvling all that fast the the first question is, what am i doing wrong?
We don't know your Setup.
But if you are possible grind with your 70er Char Instances.
At Dualboxing QuestXP > KillExp (and because of the highChar)

the other thing is, it gets rather annoying to keep rolling myself back and forth between pcs to pick up quest item loot, its rather annoying and frequent, is there a way for my alt to loot while i stay on this pc? like an autoloot or something of that nature?
No, no way to Automate something.

so what do u think, 1pc or 2? and why?
2 Pcs because of
my pc isnt the greatest a few years old, i can play wow on med-low settings fine /sigh
I use 2 Pcs, too.
I use 2 Cable-Keyboards, 2 CableMice and 1 Wireless keyboard with 2 receivers.
So I Can control my Chars allone (because of Whispers, Makro changing,...) and simultan.

My biggest Problem is/was to synergice the two Keyboardsettings.
For example 1-4 is for the main and 5-8 is the clone and 9-´ are the keys with funtions for both chars.
And also the Runningkeys (wasd and the arrwokeys) and my spreadout/Stop follow key....

Beginners Guide 2 Dual-Boxing (3,4,5 boxing)
In this thread, the Pdf is very fine and i think it helps alot.