The gro clock might not have worked, but there is no count-down sign for showing how near to getting up time is on.
I would recommend the kid-sleep clock.
www.amazon.co.uk/Claessens-KidSleep-Sleeptrainer-Nightlight-White/dp/B00C0XNITU/ref=sr_1_1_a_it?ie=UTF8&qid=1495557078&sr=8-1&keywords=kidsleep&tag=mumsnetforum-21
but you do need to have a whole plan, and she is old enough to talk her through the new plan. Put the clock on top of a cupboard if necessary to keep it out of reach, we put a shelf on the wall high enough to serve the purpose.
You need to provide a small drink, some books and soft toys that she is allowed to have in bed, but she must not get out of bed before the bunny gets up, then she is immediately allowed to come to you.
The first night set the alarm to be near her natural waking time, and get up with her, the next night set it 15 mins later, and progress slowly making it a later time til she is getting up at a time that is acceptable to you. If she is into reward charts (not all 4 year olds are!) then utilise this at the same time. Or just plain old bribery, if it helps!
Have clear consequence of if she gets up before bunny is awake, returning to bed with no conversation each time. But big excited fuss and reward any time she is in bed when the alarm goes off!
It takes persistence and time, but it will work.
Aim for her getting at least 12 hours sleep in the day, (with or without an afternoon nap) The clock I have put a link to here, has a nap-time setting too. With or without a gentle wake alarm. For me the nap had to be limited for older children, so that they only had a brief 30 mins nap shortly after lunch to get them through til bedtime, and only if they needed it.
If you just put a lock on her door you will not solve the early rising, she will just up the ante with making as much noise as possible in her room (banging on door etc!!!!)
There is no quick solution, but it can be solved.