Well, since Cyndane isn't as powerfull as she used to be when she was Lanfear is something that made me think that.  And since Aran'gar showed up, you can assume that the ability to channel is tied to the soul and not the body.

So appart from the DO limiting her (maybe as a punishment inspired by her treatment of Asmodean), you can also speculate that being reborn like this shewas just reset at her original strength.

The fact that she was searching for a new, bigger source of power when she made the bore indicates that she was activly seeking power.  Power and glory are her biggest drives.

Add to this the fact that the portals were transported just after the breaking (which makes me assume they were made during or before the age of legends)gives the possibility for her to have visited them and proves that at least some Aes Sedai and their Aiel knew about them.

The fact that her beauty is described the way it is also gives me the feeling it points in this direction.

You are correct, no evidence, but at least there's a motive and that spurred the idea.

But if RJ said they couldn't powerboost, I guess that theory is shot down.  But you asked for the reasoning and that was it.

Is it possible Lanfear, prior to making the bore, visited the Eelfinn and asked to be the most beautifull, the most powerfull and a way out?  And the Aelfinn to find out where she could find more power and finding the bore?

Sorry, but the site is a bit too massive to go and look whether that theory is already around.  Would explain why she was killed when entering that gate.