What do i do about a clingy Friend?

I have a friend and she/he smoothers me. She expects me to spend every min of every day with her and she doesnt seem to realise that i have other friends and would like to spend time with them every so often. But everytime i go out with other friends she/he invites themselfs out with me and my mates. Does my head in because its al the time. I have peed suttle hints to her/him to get the picture but they dont get it. Like they are a good mate of mine but i want them to lay of just a bit do i can spend a bit of time with other mates. I dont want to lose the friendship but i hate this fact. Should i tell them bluntly or gently? Or in person or tell them over msn etc then continue in person?