Answer: Containing an 18 month old toddler in a bed can be a challenge. You may be better leaving her in the cot until you can reason with her and she understands that she needs to stay on her bed until she goes to sleep. Of course this all depends on your individual needs and housing arrangements, I appreciate that.
The majority of parents just transition their toddlers straight from their cot into a normal sized bed. This depends on money and income and a myriad of other factors, but in terms of practicality there’s lots to be said for them going straight into a normal sized single bed.
You can get bed rails to fit a standard single bed, investigate your options. They are a good idea, especially in the early months of transitioning (otherwise a mattress on the floor in case the child falls out of bed). Rails help the child to develop a sense of where they are in the bed and really do help to reduce bed related trauma. Just, for all reasons, avoid investing in a bunk bed. They are too risky and dangerous for all kids.
Cheers
Jane