Many Ashkanazi women have the minhag that on Yom Tov night they light candles and make the beracha for Yom Tov and then also the shehichiyanu, even though the husband recites shehechiyanu at kiddush. Isn’t the shechiyanu (answering amen) a hefsek between the 1st bracha and drinking the wine? Furthermore, isn’t shehichiyanu ideally supposed to be made over a cup of wine, though it can be made theoretically at any time during Yom Tov?
Although Mishna Berura (263:23) writes that it is preferable for a woman to make shehecheyanu during kiddush rather than at candle-lighting, it is true that many have the custom of reciting the blessing after lighting the candles. Poskim discuss why answering amen is not considered a hefsek, and Rav Moshe Feinstein (Orach Chaim, vol. 4, no. 101) has written that because the shehecheyanu is part of kiddush, answering amen does not constitute a hefsek even if the woman has already recited the blessing. He applies the same logic to the blessing of leishev basukka.
Sources: See also Ben Ish Chai, Noach, no. 10; Shevet Halevi 3:69; Har Tzvi no. 154; see at length Edus Beyaakov, no. 118.