I think she is absolutely right, I have been doing something similar for years, not for any worthy environmental reasons but because when you work full time, have two children and a DH who is away a lot, you cut any corners you can find, or at least I did and limiting the number of times clothes were washed and then, where necessary needed ironing, was a real time and hassle saver.
Pants and tights/socks last one day. Bras several, nightdresses a week. After that it is a question of a visual inspection and sniff after each wear, until I decide a wash is needed. use deodarent thoroughly, and tops shouldn't need washing after each wear, unless you are a sweaty individual - andI know some are.