when should i dual her to a mage (which lv)?

Depends on whether you've got TotSC or not. If you have it, I'd recommend dualing at thief level 7, that way you can still get her to mage level 8.

i dont have totsc which lv now?

Dual her at level 6 then. That's the highest you can go as a thief and still reach one level higher within the XP cap of 89,000.

when im on the mage lv`s under my thief lv how should i do whit the lock-pickin and all that?

This Is Why I Don't Like Dual Classing. You Can't Use The Theif Abilities Until The Mage Side Takes Over The Theif Side In Experience! Have A Multiclass, Or A Single Class, Never A Dual Class!

<blockquote>quote:</font><hr>Originally posted by cloud88:
when im on the mage lv`s under my thief lv how should i do whit the lock-pickin and all that?<hr></blockquote>

One thing you could do is hire another thief for the duration. Safana, Coran, Alora, there are plenty around.

Another solution is to try to avoid lockpicking etc. altogether and try to amass enough XP by traveling around and killing monsters on those random encounters. That's gonna take a long time though.

IMO I Recommend Coran. He Is The Best Theif On The Game!!

A few ways of working around the lockpicking dilema are
1) suggested before, get another thief
2) cast knock. I'm not to sure of the level so it might take some time to get to the point where you can memorize it
3) bash them. A strong enough character can bash locks
Most, if not all critical game items are in unlocked chests though, but the locked ones can contain some usefull items, so i would suggest one of the above or just go through the game anyway.

How do you bash locks?