Woman is signed like Mommy/Mother/Mom, but with a variation to the sign. First, touch the thumb of your open, dominant hand to your chin, while the rest of the fingers are spread out. Then bring that same open hand down to the center of your chest.
Teach the woman sign to your toddler, as it may be a tad too abstract for your baby. It could help to sign woman along with mommy, aunt, grandmother, or any other adult female that your child is introduced to. Eventually, they'll catch your drift.
Teach the woman sign to your toddler as you introduce other signs relating to adult female figures that they may interact with regularly.