Happened to my baby as well. At first I thought it was colic too or reflux. We also upsized his teat size. With frequent burping his condition improved. Just try to burp her before feeding her again. Can continue size 1 coz if the flow is too slow she might have to suckle very hard and swallow in more air. But you can still control the flow by lowering the milk bottle
likely colic. can try going back to 0 cos the flow may be too fast