We will begin by examining the halachic indications in a situation in which there are no extenuating circumstances, and we will then turn our attention to the best solutions in cases of need.
The gemara[1] cites a machloket regarding whether one who ate before making Kiddush may still recite Kiddush afterward. We accept the opinion that he may, but we also accept the gemara’s implication that it is forbidden (Rabbinically) to eat even small quantities before Kiddush. [2]
When does this prohibition begin? The poskim assume that it is forbidden to eat once it is possibly Shabbat (i.e., from sunset). In addition, it is forbidden to eat even earlier if one has already accepted Shabbat.[3] Since (at least Ashkenazi) women accept Shabbat when they light Shabbat candles,[4] most assume that it is forbidden for a woman to eat or drink between lighting candles and hearing Kiddush.[5]
The Dagul MeiRevava[6] writes that whereas davening Ma’ariv makes it Shabbat with regard to all Shabbat prohibitions, it is questionable whether other forms[7] of accepting Shabbat early obligate one to adhere to all Rabbinical laws.[8]
The Minchat Yitzchak[9] entertains the possibility that it would be permitted to eat after candle lighting before Ma’ariv. However, he is unwilling to be lenient in practice in the absence of other reasons for leniency (such as the case he discusses, in which one is drinking water to swallow medicine).
Prohibitions of eating before performing a mitzva generally do not apply to drinking water.[10] This is the case, for example, when it comes to the prohibition of eating before Havdala.[11] In contrast, however, it is forbidden to drink even water before Kiddush.[12] The Rosh[13] explains that this is due to the concept that any eating done on Shabbat, including the drinking of water, has special importance. There is a machloket regarding whether this concept applies during bein hashemashot,[14] and it is thus unclear whether one may drink water during that time period.[15] In the case of a woman who is thirsty to drink water, the Shemirat Shabbat K’Hilchata[16] is willing to be lenient only until sunset.
As mentioned, the reason it is forbidden for a woman who lit Shabbat candles to eat is that she accepts Shabbat at that time. There is a general consensus that at least conceptually, a woman can explicitly have in mind not to accept Shabbat with her lighting.[17] In practice, however, poskim rely on such a condition only in cases of significant need.[18] Along these lines, Shemirat Shabbat K’Hilchata[19] allows a woman who is feeling weak or who is nursing to eat if she feels she needs to, even after candle lighting, if she made a condition not to accept Shabbat with her lighting.
However, these leniencies of the Shemirat Shabbat K’Hilchata apply, as a matter of course, only if the woman finishes eating before sunset. What if a woman becomes particularly hungry after that point, as commonly happens when one is nursing? Although there are significant leniencies for nursing mothers to ensure that their milk supply is not affected, waiting an hour is unlikely to affect one’s milk supply. It is true that in many cases, a woman who nurses may suffer particular distress if extreme hunger hits her. Nevertheless, it is generally difficult to be lenient, because there is almost always the alternative of the woman reciting Kiddush before her husband comes home.[20] There is no halachic reason for her not to do so if she is able to arrange for the requisite eating after reciting the Kiddush.[21] Even if it is not accepted in your family for a woman to recite Kiddush, a simple discussion with your husband, including the pertinent halachic information, should hopefully convince him that your making Kiddush is better than eating or drinking after sunset before Kiddush.
On the other hand, every rule has exceptions, and when there is an acute need, one may be lenient after sunset as well, especially in regard to drinking (even large quantities) of water.