The age gap doesn't matter - you're both adults.
I would say two things (and as you don't know me from a bar of soap I can be frank):
Don't worry about your "friendship" any longer because there won't be one - not properly at any rate. You have developed genuine feelings for this woman and as long as they go unaddressed, you will not really be able to go back to a pleasant chat over tea and biscuits, no matter what the magazines / films / advice columns might say. Sure, you might be able to maintain the illusion of a "friendship" but it won't be real.
Secondly, regarding making a confession, it's better to regret something you have done rather than something you haven't. I say tell her. What's the worst that could happen?
All that said, workplace romances are not a great idea in my experience, but if you think it's the real deal, then why not?