Bridal sizing runs smaller than the street size you are used to, and gowns are ordered to your actual measurements rather than to a size on a tag. This is completely normal and it is not a reflection on you - we would rather tell you now than have you discover it for the first time in front of an audience.
Nearly every gown we sell is altered afterward - that is expected, not a sign something went wrong. Alterations are priced separately from the gown itself, typically a few hundred dollars depending on how much the dress needs, and we walk through that cost at your first visit so nothing shows up as a surprise later.
Bring two or three people whose opinions you actually trust. It is tempting to bring everyone who wants to come, but a crowded room of competing opinions is the single most common way a bride talks herself out of the dress she loved. Decide your budget before you arrive, too - we only pull gowns inside the number you give us, so the whole rack stays something you can say yes to.
