Blankets for 21 month old

My 21 month old has stopped sleeping well especially the initial going down . I gave her blanket last night and eventually settled. She has separation issues with sleep. Can I wrap blanket around her and leave as that? I hear people say to tuck it in sides of cot but that won't work with her as she likes to be able to move freely . Hates being restricted. She had to fall asleep on me first so thought maybe wrap blanket round her