The same is not true of the she’hechiyanu said between kiddush and drinking the kos. Chazal instituted that the bracha of she’hechiyanu be recited over a kos, therefore, adding she’hechiyanu in that context does not constitute a hefesk. No such takanah was ever made with respect to candlelighting. (Rav Shternbruch says a huge chiddush. Chazal instituted saying she’hechiyanu over a kos to add to the chashivhus of the bracha. For women, lighting candles has the same chashivus as kiddush does for a man, and therefore, they are justified in saying the bracha then.)
R’ Ovadya Yosef (Yechaveh Da’as vol 3) adds that kiddush on the second night of Rosh hHShana, where we insert a she’hechiyanu on a new fruit into the nusach of kiddush, is also no proof to anything. M’ikar hadin we pasken that even if someone did not have a new fruit, he would still recite a she’hechiyanu on the kedushas Yom Tov. This kiddush is no different than any other.
The one source that I found that seems to open the door to the argument for there being no problem of hefsek is a Mishna Berura in Hil Yom HaKippurim 425:5. Although the Beis Yosef holds that there never recites the bracha on besamim in havdalah on motzei Y.K., the majority of Achronim disagree. The M.B. sides with their view and adds that there is no danger of bracha l’vatalah because the bracha is a birchas ha’nehenin and bottom line, one does enjoy the fragrance of the spices. What the M.B. does not directly address is that fact that if the bracha is unnecessary, it should be a hefsek. Does that mean hefsek is not an issue, so long as the bracha is not levatala? Or maybe the M.B. is just not overly concerned here because he thinks the other Achronim are right and the Beis Yosef wrong anyway?
As a way to have her cake and eat it, to say the she’hechiyanu at the time of hadlakah but to also avoid any problem of hefsek, my wife was given an eitzah years ago by her great-uncle, R’ Yosef Holzberg. Instead of saying the she’hechiyanu in between the bracha on hadlakas neiros and the lighting, she says the she’hechiyanu immediately after lighting. I thought this was a brilliant idea, but had two cents to add: you can get even closer to keeping the minhag of saying she’hechiyanu before lighting by sandwiching the she’hechiyanu in between lighting the first and second candles. Since m’ikar hadin you only need to light one candle, once you are past that point the issue of hefsek is gone, but at the same time, the she’hechiyanu is still on the act of candlelighting. (I haven't asked anyone what they think of the idea.)