Hi everyone. Going to keep this short and sweet as possible. Any opinions on this situation is greatly appreciated!

My sister (P) had a best friend (L). They were best friends for a few years. P would always tell me how much me and L had in common and how much we'd get along. About 2 months ago L added me on social media. She replied to something I'd posted and the conversations started from there. As my sister had predicted, we got along well. We chatted about random stuff and the conversations were lighthearted. At the time i wasn't at home (I'm a student) so i was excited to tell my sister how well me and L were getting along once the holidays came around.

When i came home for the holidays, the conversation didn't go as i expected. According to my sister, she'd made the decision to stop speaking to L the week before i came home, which i wasn't aware of. She explained that she'd gotten into an argument with a friend of L's, and she'd decided to stop speaking to both of them. However, she also said that her decision to stop speaking to L was because of L's association with this other person, not because L did anything to my sister personally. I explained to my sister that earlier that day, before our conversation, I'd already agreed to meet L today for a coffee. When i told my sister this, she admitted to feeling a little upset with me, and told me i should cancel plans with L in 'solidarity' of her decision. She also tried to persuade me to cut off L and suggested i pretend to be sick so I'd have an excuse to not meet her. She admitted her feelings were slightly rooted in jealousy, but the whole thing was pretty uncomfortable. After a few days of thinking i decided i was still going to meet L, but now i feel extremely guilty.

(going to re-emphasise that me and L started bonding before my sister cut her off, if it was after I'd be more suspicious of L' s intentions. L didn't hurt my sister personally, my sister only cut her off through association.)

I don't intend on becoming best friends with L, but i feel conflicted because i feel like I'm being expected to give her the cold shoulder out of solidarity for my sister, and as much as i care for my sister, I'm unsure whether that's a fair thing to expect of me when L wasn't the one that my sister fell out with.

AITAH?