Well I mever said that he has the right of demanding an abortion or that this not on him. She asked a serious question over morality and ethics and I am doing my best on taking it seriously and seeing it from all perspectives (for me, it is her body and her choice, but she is asking over moeality).
About the no strings attached, she mentioned she met him on tinder, that it was a casual relationship. I don't know how that works as I have never being in that situation, so if I am wrong I apologize. But to my understanding, people don't go to a casual encounter expecting a long term relationship or children (i am not saying he has the right to demand anything from her, just that there is the implicit agreement of maybe we see each other again or maybe not, so lets not have a child on our first meeting). I believe by what friends have experienced there, that it is a no strings attached situation. Again, I have no experience in this. But this is a questio over morality, so I will try my best. Both as consenting adults and she said that both accepted the not use of a condom (of course, if she was not tricked or coerced, which she says in the comments that she was not. She a cepted the no use of a condom. She also says that she was not looking to become pregnant, even if she would like a kid. So both were not looking to have a kid), but by not using a condom, they both accepted then the less than 1% possibility of a child, the moral dilemma she is asking about now, and of course, the fact that maybe he got her a disease. All that they both accepted when they decided to sleep together and both accepted not to use a condom (because, talking over morality that is personal, and medicine... having a kid is not the worst thing you can get from unprotected sex and the both took the risk) I am even going further. What I find complex is that this dilemma can go further. If he had sifilis or herpes, and both consented to not use a condom, and she gets sick and her baby gets it while being given birth and he survives with long lasting consequences... could she sue him or ask for a pension (even if she told him she won't need anything), even if both as consenting adults agreed to not use a condom? Did she accept the risk on her potential kid (that according to the comments, they both embraced from the moment they both accepted to not use a condom)? I would like to think that she didn't, because I am thinking on her and her baby . But i would like to think that he did. So it makes no sense I am being partial to her and her baby. That is why "morality" questions are difficult and complex (maybe more than ethics).
What I find complex is to caluate morality for others, as it depends on each person. And placing the same judgement in similar situations derived from the decision. Like the troley case. Ask any philosophy professor, it has no real solution. Obviously the fact that it is her body and her choice is not complex at all and it should not be on discussion (and from what I understand, it is not the point).
My conclusion is, this (morality, not if it is or not legally or biologically her choice), is not something to ask others. Moral is personal and something she needs to talk to the biological father. They are both the only ones involved in this "is this moral or not" decision and derivates (is he sick? Is she now with a disease? Would the baby be affected? Does any of that changes the morality of other decisions?)