Why would my ex girlfriend roommate unfriend me?

My ex girlfriend dumped me about 3 weeks ago and her and her roommate still follow me on Facebook. I have not talked to her (or her roommate) since the breakup. A few days ago I posted a picture of myself skiing and her roommate 'liked' it, a couple days later (today) her roommate removed me as a friend. (My ex has not unfriended me)

I only met and hung out with her a couple times with my ex but I just thought it was pretty random. Any thoughts as to this behavior?
Why would my ex girlfriend roommate unfriend me?
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