I have the same problem as you, quite short and my son got too heavy,  we got a cot that turns into a toddler bed the cot sides come off and you put and extra bit on so your child can't fall out.  We changed the got to a toddler bed when my son was about 2 years and 2 or 3 mths

My health nurse told me that they recommend that kids stay in the cot as long as possible.

Hi, i recently bought my daughter a single toddler bed which has sides so she cant fall out. she was 16months at the time now 18 months, and slept in there very well for her day sleeps, as she is currently in our bed (never took to her cot) i figured because she has always been used to a bed shed take it easy to having her own! but i still havent put her in of a night starting tomorrow though and no turning back as i have only 7 weeks to go and ive got a new bub so i really want her out of our bed! but i think if you were to get her her own  bed and try day sleeps at first it will make it a bit easier on you to get her in of a night so she knows its not that scary!

Hope this helps jodie..