Wow, since seeing the screen shot of the tiktok comment I just can't help but think what a sad state of affairs.
Having your first serious relationship is a big thing, it is a lot and a complete lifestyle change - it is natural to have somewhat of an affect on any friendship.
Seeing as Syd & Ell have spent the majority of their life's together, but in that time Syd has already had a serious boyfriend - I can assume that Syd is not used to Ell having a boyfriend around and not having Ells attention / neediness, its also very likely Ells boyfriend didn't warm to Syd (like alot us) and this has caused friction on spending time together, etc.
It is very, very sad that a 20 year friendship has come to an abrupt end because of relationships. I really hope that this is not a case of Syd being jealous and wanting that control but she really isn't portraying herself in a better light.
If this is the case it puts Ell in a very hard position, of course friends come first but everybody deserves a life partner and happiness.
So unfortunate it has come to that but I do hope that they see sense and write a somewhat truthful statement to all their young, easily influenced audience.