Stuart Sutcliffe met Astrid in 1960 in Hamburg, Germany while the Beatles were performing there for a number of weeks. John wrote a lot about Astrid in his letters to Cynthia who got jealous until he announced to her that Astrid and Stuart were in love. Cynthia and Astrid met in 1961 when Cynthia and Dot traveled to Hamburg to visit John and Paul during her Spring holiday from Liverpool Art College. Cynthia stayed with Astrid while Dot stayed with another friend of The Beatles' and they became great friends, spending a lot of time together while the Beatles' played and rehearsed. In 1963, Astrid was with friends in Paris, France when she heard that John and Cynthia were having their honeymoon so they got together. In 1964, Astrid traveled to London while the Beatles' were filming 'A Hard Day's Night' and visited Cynthia. Astrid also met Maureen (and Pattie) on the set of 'A Hard Day's Night'. Cynthia and Astrid remain in touch to this day.
Paul met Dot at the Casbah Club in Liverpool, England in 1959. Dot and Cynthia quickly became good friends, sticking together wherever their boyfriends were playing, and traveling to Hamburg where they met Astrid. In 1961, Dot moved next door to Cynthia's apartment until the following year when she and Paul broke up. Dot and Cynthia remained friends until she moved to Canada in 1964; they didn't see each other for several years until the 1990s.
It's not known if Dot and Maureen knew each other- however they were both frequent regulars at the clubs in Liverpool whenever the Beatles played so it's very possible that they knew each other as acquintances.