Ebf mamas

Do you feed baby on one side until they are content? My LO is 12 days old and feeds from the right boob for well over 20 minutes.. she takes herself off but after a while. If I take her off she is upset and pokes her lip out and starts to cry. I switch her to the other breast and once she’s eating she’s fine but I have to literally pull her off at 20 minutes maybe she’s using me for comfort at that point.. also she acts hungry after feedings and she’s very well getting enough. I feed her again if so and she throws it up so she’s just over feeding herself bc obviously I can’t really know until I try giving her more milk.. what should I do?