Probably just over fed , maybe your mom just needs a little refresh for bottle feeding? It's not the same as formula and baby gives very subtle clues as to when they are done. Otherwise they will keep eating until there isn't anything left and just spit it all up . They aren't able to connect that full means to stop eating until they're about 3 months old or so.As long as she's keeping her meals down for the most part it should be okay:)

a baby will always eat as much as they want. they'll stop when they're full so if your baby ate that much it's fine just watch for throwing up a lot

My daughter only ate about 2 oz at a time til almost a month