Question

she can be a bit of a handful sometimes

Answer 1

او بعضی وقتها شیطنت‌هایی/بدقلقی می‌کند.

بعضی وقت‌ها بدقلق می‌شود. 

Comments

+١

اون بعضي وقتها مي تونه يه كم غير قابل كنترل / بدقلق و اذيت كن  باشه. 

Handful: 

informal A person ( often a child) or group that is very difficult to deal with or control:
the kids could be such a handful.
The hyperactive toddler is a real handful.

http://www.oxforddictionaries.com/definition/english/handful

http://dictionary.cambridge.org/dictionary/english/handful