Elsa is definitely one of the main LI. MC will, for sure, have to make a choice between his fantasy crush and Elsa at some point.
there are many signs. and MC, through the player choices, can add some little gestures that add up.
she might already have feelings for him too. he is the only one she shows her real personality to. and it isn't because she thinks he is harmless and insignificant, as there are others in the company that are like that and she still has her guard up with them, like Matt and the friend that introduced her to the company.
also, MC met Alice and Elsa the same day, and his change began on that day. there is a chance Elsa saw his potential and will the first day, and thought the changes he began was because of her. but then MC revealed it was because of Alice, and she still wanted to help him reach his potential, and hoped he would get over his crush by the time his transformation is over.
she doesn't need MC at all to have a very successful career. even if it is a bit quicker to get there with MC, it's still a ton of effort, time and even more risks. it's not really worth it, in the grand scheme of things. she could easily ride her family's connections and money to get to the top.
maybe she helps MC because she is just bored with life. or because she likes him a little bit without acknowledging it. or a little bit of both ?