Oh man, I know that urge to nurse a baby who is not yours, but clearly needs and wants some nursing time. 
If she has a hard time nursing, too, that just adds to the stress exponentially. To her, if she has been wrestling/struggling with a frantic baby who won't latch, or who latches badly, and she's been trying all day, and it's been a few hours since the baby ate, and she sees that the baby will take the bottle of pumped milk peacefully, then yes, that can seem easier.
She may not know that the weeks of hard work and struggle would pay off in the end, and nursing would end up being so much easier.
If she has a hard time nursing, too, that just adds to the stress exponentially. To her, if she has been wrestling/struggling with a frantic baby who won't latch, or who latches badly, and she's been trying all day, and it's been a few hours since the baby ate, and she sees that the baby will take the bottle of pumped milk peacefully, then yes, that can seem easier.
She may not know that the weeks of hard work and struggle would pay off in the end, and nursing would end up being so much easier.
