Okay, so I finally got around to looking up some of these halachos in Shmiras Shabbos K’hilchasa:
1. You fulfill your obligation with one candle, but it is a Mitzvah to light more, and the Minhag is to light at least two. (43/2). (from the way it’s phrased, it sounds like it may be a bigger Mitzvah to light a lot of candles.)
2. You should not light a candleholder that has 7 branches made of metal (43/2). (I never heard of this halacha before!).
3.If you are accustomed to lighting a certain number of candles, you are not allowed to light less. (43/3) This only applies when you are lighting in your own house. If you are away, the minhag is to light two candles.
4. If you are accustomed to lighting big candles, you can’t light smaller ones. This also only applies when you are lighting in your own house. (43/3) (this was also news to me!)
5. If the wife wants to start lighting more candles, she is only allowed to do so if her husband doesn’t mind (43/3). (there’s the answer to your question, LB!)
6. If she forgets to light, she has to light one extra candle every week (43/5).
7. If she forgets more than once, she has to add one candle for each time that she forgot (ibid).
8. If she is poor, it is enough to light bigger candles every week or use a little more oil (ibid).
9. This halacha only applies if she FORGOT and not if she is “ones”/coerced (ibid). (so it would seem that someone who couldn’t light because she was asleep would not have to light extra – but she should ask a sheilah to be sure).
10. If she didn’t light because she made a mistake – either in the halacha or the reality – it is not clear what the halacha is and it is possible that she doesn’t have to add on (ibid, footnote 36).
11. If the candles blow out, she doesn’t have to add on, unless she could have relit them and didn’t. If it was Yomtov or if it’s Shabbos but she wasn’t mekabel Shabbos yet and it there was still time to light before Shabbos and she she didn’t, then she has to add on a candle in the future. If she was mekabel Shabbos but she could have asked someone else to relight the candles and she didn’t, it is a question if she has to add on in the future (ibid).