Fork for 105lb rider, 4"-5"

I think you will find a lot of threads that ask the same question. Just do a search for 'light rider' or something.

My one piece of advice is stick with an air fork. With a coil sprung fork it's hard to find coils that work with that light of a rider.

Marzocchi 44 TSTMicro
Fox F-Series RL
Rock Shox SID or Reba

Try a Manitou. Most of their air shocks use an air/coil system and you can get a light spring for her that should work well. TPC works well and can be tuned easily for her as well.