Is this gross negligence or am I over-reacting?

[thinkofthemoney]

Hello, can anyone help - nanny or employer?
We have had our nanny for just over a year. I have never gelled with her and there have been a few minor teething issues but she seems to take good care of our two children (2 and 4 yrs). They never seem overly happy to see her or sad to see her go but happy enough IYKWIM.
Anyway, today a neighbour we know to say hello/chat to called round almost in tears. She said she was unsure whether or to to tell me but 2 weeks ago she was walking her dog at the local river and saw my 4 year old dd sat on a wall directly bordering a very high lock (loch? sorry about spelling!) all by herself.
She ran over as she was leaning backwards and thought she was going to fall in. It is about a 10 foot drop into deep water here. She was looking round for me or my husband but no-one was to be seen. By this time a small crowd had gathered and then about 5 mins later (she can't be sure but says it was some time) our nanny came running from out of sight at least 150m and from behind a very heavy gate (the kind to keep cows out).
She then really told off my daughter for disappearing and the neighbour was quite cross as she felt our nanny had placed dd in a highly dangerous position.
The nanny had been chatting with another nanny friend and obviously hadn't realised dd was missing.
Our nanny has never mentioned a word of this to us.
Now I feel sick that if the neighbour had not been there our daughter may have fell in. A long time ago the lock keepers son of a similar age fell in and died.
Now I never let my children out of my sight around water and my initial feeling is I can not trust her to have my children again.
Clearly I need to get her side, however our neighbour has no reason to make this up and it was obviously quite distressing for her to tell us - she did not want to cause trouble as she realised it may mean our nanny losing her job.
So do you think this is a sacking offence? I'm not sure I could trust her again and am wondering if there have been other instances she's not told us about.
It is also going to be a nightmare getting childcare over Christmas - there is no way I either of us can take time off work and we have no family so I need to be sure if sacking for gross negligence is the right thing or not.
Opinions gratefully recieved - thanks for reading of you have reached the end!

Given the timing, personally I would weigh up the likelihood of her doing something that results in an accident between now and the new year (which is no more or less than it was last week) and as long as I felt my children would not be exposed to an unacceptable risk, dismiss her (with pay in lieu of notice) in January.

have to say though at the end of the day as a cm its my above all else duty to keep the children in my care safe, bugger learning journeys, obs and planning, above all keep safe and out of harms way so can see exactly why you are deciding on this action and of course if the trust is gone its gone!!

best of luck as a horrid situation for you and dcs

Poor you, what an awful situation. I've had something similar happen when my children were younger and apart from all the worry etc, there are the practical issues. If you decide to let the nanny go - how do you find acceptable childcare at short notice - the week before christmas! I feel for you.
Agree with other comments - get the nanny's side of the story first. But ultimately, your description of the nanny at the beginning of the post sounds like you wouldn't be too sorry to see her leave.
Start looking for another nanny - even if you haven't decided yet to let your current one go. The most important people in this are your children.
Best of luck.