In her cot, or in your bed?
Mine slept in my bed with me, and never had pillows on 'their side' of the bed but did end up sneaking onto mine by 18 months. If she's strong enough to move things off her in her sleep and there's no way anything could get trapped on her face (side railings etc), I'd think you'd be okay. I believe standard advice is from 12 months?
If she's in her cot, don't use a full-sized pillow. You can get small, flat 'cot bed' ones. Could buy one for her to have if she's co-sleeping with you, too, I guess!