Maiden milkers are fine, but they will not milk to their full potential until they have actually had kids themselves. Be cautious- if you want to put her in kid for next spring, and you milk her heavily from now until the autumn during the period when she should still be growing, you will place a strain on her calcium levels.
You are fortunate she is that bit older- she may well be fine. We try and not milk goatlings unless absolutely necessary- ie udder hot or too tight with milk.
If you want to encourage in the milk, then yes, milk her twice a day and increase the concentrates slightly. It is a common thing to happen at this time of year, days getting much longer, and some nice spring grass coming through.
Beth