Hunton bridge to Hemel Hempstead

I have been riding for 4 weeks ( after an absence of 37 years) and have set myself a target of riding from my home in leavesden to my office in Hemel Hempstead. I have worries about getting to hunton bridge ( it's all downhill, which means of course it's all uphill too!) but have looked at various route mapping sites and it looks like I may be able to ride the canal path all the way to hemel. This is a big deal for me, in fact I can't even believe I have decided to do this but the idea of getting fit, saving money and saving the world is appealing. But is it safe for a lone woman ( only ever likely to ride in good light conditions) to ride alone on this track? Has anyone any experience of this route? I have a giant expression hybrid bike and am doing 7-8 miles a day on the cycle paths/park around my home so feel I should be able to do the 6 miles or so on this route ( although I am really unfit on hills) I do occasionally have to go on the road ( rarely more than half a mile) , when the cycle paths end, but I am too worried about riding on the road to hemel as it is extremely busy. Any thoughts?