Buy an inexpensive Android phone.
While all Android phones look pretty much the same you can specify "Easy Mode" when setting up the phone which gives a simpler layout with less icons.
Then once she is used to the phone you can maybe switch off Easy Mode.
Also you can switch a "normal" Android phone to Easy Mode as shown here:
http://www.samsung.com/uk/support/skp/faq/1064814
You say you don't know much about phones so sorry to be technical but try to avoid a phone with only 16GB (Gigabytes) of memory.
Memory is used to store all the software on your phone plus videos and photos but it is very easy to run out of memory with only 16Gb.
One with more memory will be a little more expensive but it is worth getting one with the extra memory (maybe 32Gb).
List of inexpensive Android phones here. The Moto phones are good value
http://www.techradar.com/news/phone-and-communications/mobile-phones/best-cheap-smartphones-payg-mobiles-compared-961975