Oh the irony - Spoilers -
Although it is clear that sleeping with Bebe was the only way to ensure the abortion went ahead, is it not slightly ironic that presumably no contaception was used and so Otilia risked going through the whole process again but this time for her own abortion.
And for the record I think it was presented as both of them had to sleep with him. Hence the fact that Bebe told them to decide which one of them is to go first.