On the silver hair transition there are many sites that have tips and ideas as well as hairstyles that your Mom can print thank about and look at. She is lucky to have hair that looks thick. These sites are VERY upbeat and thrilled about gray hair. It Going with the skunk stripe is a rocky road that with her length will take about 3 years... even with the cut. It is a tough go.
Tell her to join Cafe Gray, and on FB there are numerous, Going Gray, Looking Great , Gray and Proud, and Going Gray and Loving it.
There are valuable resources for makeup tips, with a big focus on brows on the last one. There are several bloggers that are great as well. The trick is to stay away from anything that looks remotely like the Queen Mother or Queen E. herself.
On the bra... I think her current bra looks fine. I wish I could look as good. You need to go to a bra shop that specializes in bras. They have other clients in her age group... and they should be able to find the right bra. The RIGHT bra can make a huge difference in how one looks in clothes and in how she feels. It is worth to spend the money on this I think.
The makeup I am not that up to date on. I think others here have a much better idea of "natural" or "organic" makeup.
As far as non-frumpy... the gals here know best and those ideas from Inge are fantastic. Really great.