Sybil's biggest barrier in terms of finding other avenues of useful, good paying work is her lack of education. If you recall, governesses are only good for learning French and how to curtsey and the Granthams never sent their children to school. So while she's bright and uses her mind to consider and make carefully considered decisions, if she wants to not just work in a factory, she will need to go and further her education first. If that's the case, can she and Tom afford for her to a) not look after the child and have to pay someone else to do so and b) can she afford the time to do the learning necessary to bring her to a point where she could consider for example going to medical school to become a doctor? Even if she wants to be a teacher, she will need to bring her skills up to par in order to learn to teach a class.
I can listen no longer in silence. I must speak to you by such means as are within my reach. You pierce my soul.
I am half agony, half hope. Tell me not that I am too late, that such precious feelings are gone for ever.
- Captain Frederick Wentworth, Persuasion, Chapter 23