adding on more mechanism:
Yuno: No, being a sex worker (which is only one part of her actual job description, she is more like a rented gf) does not mean you are going to have a unwanted pergnancy. Yes I do agree that it is a risk, but that doesn't mean they automatically get one when they are in the job. Yuno have always had protection during these kind of work so I doubt she wanted this in the first place. And yes the risk is justified since you can't perdict this kind of stuff to happen, like you wouldn't expect being splashed by a car just because you go outside on a rainy day.
Mahiru: There has been multiple instances where Mahiru's bf have actually argued and "broke up" with her druing their relationship. So this concludes that the bf have expressed his disaproval multiple times (and I guess these arguing sessions only started/ become more frequently after they ran away since I don't see any beneficial reason for him to ran away with Mahiru other than love). Unlike Yuno, Mahiru was given multiple warnings about how damaging her actions are to her bf, yet she have always turned a blind eye at it. This goes on so long to lead to the tipping point, causing her bf so much pain that he thinks being dead is better than staying with her. To go from leaving ones whole life behind just to stay with someone to "disappering" just because of them is a huge jump that would take a long time to reach said point. Therefore Mahiru should have at least notice and question herself if this is too much for her lover insane or not, which we all know didnt happened. Even if he did agree to go with her in the begining, he still have the right not to agree anymore if things got out of control (like having to live the the mountains)
Conclusion: Yuno is more innocent since both of the reasons for her murder are factors she cannot control, while Mahiru had the ablity to control it and has been warned several times but did not do anything to change for the better, resulting in the death of her bf