You are very right in your assumption that labeling her aggressive is unnecessary. She's not aggressive, she just seems to have resource guarding tendencies. It's
extremely common, and very treatable and/or manageable.
I would stick to just you for the trading games and training sessions for now, until she is more comfortable with humans around her prized items/relinquishing items. She obviously for some reason or another, doesn't trust your daughter as much as she does you, around her things. She may think that children are just less predictable around her chewies, and trusts you, the calm adult, more. Give her her space, and teach your daughter to always respect Molly's space.
Not only do you want Molly to trust your daughter around her chewies, and be comfortable with her enough to drop a prized item from time to time (especially in an emergency), but you want Molly to know that she is able to have time alone, and with stress-reducing things like chewies, and that no one is going to bother her. If she is to trust your daughter, and trust that she isn't going to 'steal' her prized items, she has to know that your daughter will never do that. She has to know that your daughter is trustworthy, that she won't ever take something away and not give a fair trade, so make sure this never happens. At the same time, you want her to know that it is safe, trustworthy and a good thing to relinquish prized items when asked/redirected, because awesome things happen! I would start small, as in, not with her favorite pig's ear. And start with extremely high value treats as the trade-off.
Tonight, I would have your daughter practice leaving her be, and ignore her if/when she's chewing on her chewie. Then start very slow with the exercises tomorrow. Remember to be patient with this, it's not an overnight fix, she has to learn to trust you both implicitly.