Your questions are confusing, hence the 40 hits with no replies yet. There are 5'4" and shorter women riding 29ers, so why do you think 5'8" is too short? A 29er is simply a mtb/hybrid frame that will take 700c wheels with fat tires. At 5'8" you should be thinking medium or 18" - 19" frame depending on whether they are marketed as s/m/l or 16/18/20. Are there no bike shops in Rekjavik where you can sit on different bikes to size yourself?
Just trying to open conversation here.