Id forgotten that this episode made me cry until I started crying towards the end of your reaction lol. I hope you decide to finish out the series now that you're back reacting to things! I think you'll be interested in how they tackle Charlie's journey from here.
Also Sahar reacted like that because she and Imogen have a history and they have a tense vibe established. In the truth/dare episode she says Imogen stopped talking to her when she got her first boyfriend and Imogen says it was the opposite way around. The vibes I had at this point in the show on initial watch was that they're kind of into each other but Sahar is defensive due to the fact a relationship can't happen because at least as far as anyone knows Imogen is straight. It's also just really uncomfortable having a crush on a good friend and not wanting to ruin things so you can still hang out.