Can LeBlanc Deceiver use her champion ability on Hold, with the card she draws if she was at 0 cards in hand before?

No, you cannot use LeBlanc's "Deceiver" ability if you have no cards in your hand.

According to RiftJudge FAQ #8686, the discard in LeBlanc’s ability ("...discard 1 and exhaust me to...") is a cost. In Riftbound, a cost must be paid in full to activate an ability or play a card. If you have no cards in your hand, you cannot pay the cost, and therefore you cannot activate the ability at all.

You cannot draw a card to satisfy this cost because the cost must be paid at the moment you choose to activate the ability, before any potential subsequent effects (such as draws from other sources) could occur.