One additional point I'd add to lend credence to Graendal being higher up the list is this quote:

~The Fires of Heaven


"If this Rand al'Thor really is Lews Therin Telamon reborn," Graendal went on, settling herself on the man's back where he crouched on all fours, "I am surprised you haven't tried to snuggle him into your bed, Lanfear. Or would it be so easy? I seem to remember Lews Therin led you by the nose, not the other way around. Squelched your little tantrums. Sent you running to fetch his wine, in a manner of speaking." She set her own wine on the tray, held out rigidly by the sightlessly kneeling woman. "You were so obsessed with him you'd have stretched out at his feet if he said 'rug'."

No way a woman significantly weaker throws this in Lanfears face! Just minutes later the two almost end up in a duel, if not for Rhavin we may well have seen a chick-Forsaken fight

Graendal is a lot of the things, but stupid is not one of them. We know that she will not risk facing Rand head-to-head, but she was willing to face Lanfear? Very unlikely IMO unless she was close enough in strength that she felt her skill could overcome Lanfear's power.