all my kids were aged 13-18mths when they moved into a bed - a toddler bed, with small half rails near the head....i didnt worry so much them falling out - bound to happen sooner or later (for me it was better than them jumping out of the cot!)....on the big day - we dismantled the cot, replaced with bed and that was that - welcome to your bed, no going back!
if your worried about her falling out or anything, you could put something soft on the floor to break her fall, or you could roll a doona and place on side of bed.
Good luck!!
Fiona
DS1 '04, DD1 '06, DD2 '08 & the FINAL addition DS2 '11