When is it safe to give my baby a blanket?

My daughter is almost 14 months old and growing out of her sleep sacks. She also likes to stand and walk in her crib after naps. She is a healthy little girl, walking and talking and eating and mostly sleeping through the night. She sleeps in her crib, in her own room. She does sleep with a little comfort lovey. I hate the idea of buying more sleep sacks. They're expensive. Plus spring/summer is right around the corner. Is it safe at this point to let her have a light blanket? Maybe even a knitted one with holes?