It's unlikely you're going to find this lady. You could take the female results from the 1901 or 1911 census, (probably) reject anyone married and anyone over 60, and you'd have a group of possibles - but she might have entered the workhouse using a false name - that of her mother, or that of the man who impregnated her, or a random name of someone she met on the train to Dublin. Your most likely results at this stage will come from DNA matches, I suspect.