Hi
Congratulations on the birth of your wee girl, I haven't been online for ages so missed that.
The foremilk/hindmilk thing isn't clean cut, hindmilk will be present at all feedings no matter what the length is.
Do you feel a "let down" (when the milk pours out)? It could be that Ffion struggles with the fast flowing milk which makes her frustrated. If you do feel a let down and Ffion has guzzled that then she gets frustrated you can do breast compression which is like when you would try to manually express but you do it whilst the baby is latched on - this should encourage the baby to start suckling again.
I know breastfeeding can be hard going, especially when you have a toddler as well but your baby is still newborn and her feeding will be frequent as it's not only a source of food for her, it's comfort, reassurance and emotional for her at the moment. It wont always be like this but if you stick at it it'll be so convenient and the feedings will cut down to 5 mins a time!