There are some similarities and it may overlap. If Lena wants to date Holly, she can lose her to Ivy.
But generally, Holly either stays a shy nerd or becomes a slut (assuming neither Ian and Lena date her).
I'm trying to go for the Ian/Lena/Holly route in this case. Can I still pick pick the options but discourage the more extreme stuff Ivy suggests?
There are 3 "types" of Holly in the game. One is the shy nerd, then we have "encouraged" Holly and slutty Holly. There is both a difference and some overlap between encouraged Holly and wild Holly. Encouraged Holly is usually in a relationship with Ian with Ian, Lena and Ivy encouraging her to become more bold, more selfconfident, which leads to some nice scenes. Encouraged Holly for instance can wear the more sexy bikini at the beach and still have the Schopenhauer book with her. Encouraged Holly can be, depending on the choices done, just a bit or a lot more bold.
Wild Holly is not in reltionship with Ian (at first) and becomes slutty in the partly (depends on what type of Ian we play) mistaken belief that Ian prefers wild, slutty girls for girlfriend. During the beach vacation and onward we have choices for Ian how he feels about wild Holly. You can try to start a relationship with her (according to our code gurus there is a love variable/flag for Ian/wild Holly), which will certainly impact her further development, since now she can gain what she wanted, Ian´s love. When we last saw them, slutty Holly needs a place to stay, since she finally blew up against her suffocating family. It is not a leap to propose that we as Ian can convince her to stay at Ian/Perry´s flat, if we like her.(There is already a funny scene with Perry and Emma listening at the door, wanting to know who Ian is with) It also leads to Ian thinking about looking for an own flat in the future, together with Holly.
If you go for Ian and wild Holly becoming fuckbuddies or staying simply friends, it is probable Ivy leading Holly down an even more dark path than before so far.