Noha ~ I will say that when we native speakers are searching our minds for the "right words to say," 9 times out of 10, we will opt for the single word, so in this case, most native English speakers would consider both and opt for "working" rather than "to work," simply because it covers all bases and flows better, it is a more concise verbal expression of a thought.

Edgar is right. In this case that can mean the same thing and subtlely different things. Technically, "working for herself" implies she likes the act of working, and "to work for herself" implies she prefers that to working for somebody else. But in the real world, you can use them interchangeably.

Some verbs allow both, the gerund and the infinite form, and some only one. In cases where both forms are acceptable, there is often a change in meaning. I stopped working. I stopped (something) to work on a different project. The way I learn it was on a case by case basis, which may sound tedious, but it was well worth the effort.