Let's see...
Changes her own sense of style and copies Olivia's style (look at Flossie's fits before she started living with Olivia) even down to jewellery and shoes.
Starts to lose more weight and posts pictures and videos to appear slimmer (this got much worse when she moved in with Olivia), eats like Olivia too with all those coffees and mostly vegan/vegetarian eating (if eating at all)
Dyed her hair blonde like Olivia (but to be fair this was definitely inspired by her Madison Beer fantasy)
and starts to wear heavier makeup every day (Flossie always wore heavy makeup and tan when she was going out, but since being with Olivia she's obsessed with being as dark as possible. Sunbeds I assume, which was Olivia's original jam).
Let's not forget the lipfillers she's NEVER mentioned.
Started talking like Olivia, mannerisms, catch-phrases. Like the way she talks is completely different now, kinda quicker and ditzy, interrupts herself to burp or make a random unrelated comment. Like Olivia.
She's just gone very forced and cringe because she's just recreating a character. I know everyone changes, and it's good to change, but it's like Flossie has regressed to a 13 year old who found a cool best friend and has to be exactly like her to feel like she's fitting in.