How do i deal with this clingy friend of mine?

i have this friend who seems to be overly immature (we're both 16) and is super clingy (unfortunately to me). she moved to my middle school in the 7th grade, she didnt have friends yet, so my close friend who happens to be a very sociable and bubbly person befriended her so she would get used to the new school.. for the following two years, we became the-three-musketeers sort of thing, always seen together everywhere & very close.. here's the thing, i'm more of an introvert, i prefer watching a movie at home on a saturday night rather than going out partying, while my other bestie who's the sociable one happens to be the exact opposite, being the life of any party and an easy person to talk to.. and the new girl at first was quiet (i guess thats typical for newcomers in any school) then gradually became louder in an annoying and immature way (eg, she would poke someone's *** as a way of greeting, constantly bothering someone particularty when they're busy if she's bored).. anyhoo, we get along well with each other in spite of our diverse ways.. i do realise that we make a unique combo of friends and i appreciate it a lot, actually, in thinking that most of the girls at the time were a bunch of sluts trying to get attention lol XD and we werent, we were always up to the randomest stuff..then last year, the sociable friend moved somewhere else cuz of some of her family stuff, which left me and her in our used to be trio.. and somehow after that, her inner annoyingness and immaturity came to live. she got freakin annoying. i can swear that everyone was hating her for that. one thing i loved about her was about her randomness cuz thats what we have in common, but too much often does she becomes overly immature cuz of that. the worst part is that she is super clingy to me, i undrstand cuz i was one of her first close friends in here.. she refuses to leave me alone, gets mad when i go out with other friends, even talk to other people for too long :/ i get that i might be her only super close friend, but i just cant stand the fact that she's suffocating me by clinging on to me literally 24/7!!! (on the phone, if not in school or elsewhere) i know how i am introvert, and i am trying to expand my social circle but with her being all over me i just cant, literally.sometimes i think of ditching her cuz i just cant stand her, but i cant cuz she doesnt have any other friends! ofcourse she does talk to people, but she never makes close friends with them.... i swear that i feel like punching her in the face sometimes cuz she even made fun of me and my ex calling each other 'dear', 'honey' and those stuff, i mean, she acts childish. she shares a lot of her secrets with me, most are her fantasies...but its so hard to share my secrets cuz shes not open, as u can see how she made fun of something so usual like my ex calling me 'honey'.. i have no idea how i should deal with this, i've tried making new friends for her to be friends with but they ended up becoming much too annoyed with her. i've thought of ditching her but i'd feel guilty.. i have to admit, these days, i get much too annoyed with her than happy being her friend.