No it doesn't have an effect. In the UK the equality act 2010 would make discrimination on the basis of gender unlawful in these circumstances. Other EU countries are likely to have similar statutes. There are countries where religious and cultural norms do not necessarily make gender discrimination illegal.
Despite the reply given above, "fashions" do not come into it. Women in this segment of the market might benefit from positive recruitment on the basis of their underrepresentation in the market but generally in a fiercely competitive market that benefit is probably minimal (and not necessarily unlawful either.)
I do not know (even after googling it) what an "NLS MPA" programme is? On the assumption that it is a Dutch training school and a non-MPL programme (an MPL programme would usually be tied to a specific airline) the graduation opportunities are likely to be advantageous to those airlines that the school has a direct relationship with. Obviously this is still wholly dependent on the input requirement of those affiliated airlines at any given point in time and is always going to be dynamic.
Given that others from her class have found placements, has she been back and asked why she isn't being put forward? If "top of her class" is actually indicative of her level of training assessment, she would prima facie be the sort of cadet that most reputable airlines would be pleased to recruit, particularly where that recruitment would have the added advantage of balancing the representation of female pilots.
By the sound of it she hasn't been lucky in a difficult market, but she should use the advantage that might be offered by her training school as well as whatever independent opportunities might present themselves.