<human>: I'm not quite sure if my girlfriend's hot sister "Ashley" is just friendly, or has a crush on me... I need reddit's help! I am posting under a different name than normal to remain anon.

"Ashley" is also in a relationship with a guy (25M), but keeps doing things to make me unsure if she sees me as something other than a "friend."

For instance, my GF and I were going to host a pajama party, and Ashley sends a text to me saying she is going to wear a Cheetah Print Onesie (my favorite lingerie on girls, which she knows). I respond "nice, my favorite", since I didn't know really what else to say. 

Another party we were at, my GF and I want to go on the roof to check out the view, and Ashley decides to leave BF and friends inside, and come with us to the roof. Twice.

Another time, we went on a party bus, and I was sitting w/ my GF, and Ashley sits down next to me (her BF is on other end of bus) at the beginning of the bus. I felt somewhat uncomfortable, thinking she should be with her BF, so tried to pretend I didn't notice. But when we took a group picture, she was again next to me resting her hands on me.

Also a few weeks ago she randomly sends me this text at night saying "I miss you."

Could all this have been instigated when she wore a skimpy bathing suit two summers ago, and we were sun tanning at her pool waiting for my GF to get home? Am I just over-reacting? Am I seeing something when there is nothing??

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: My GF's sister seems to have a crush on me, but I am not sure if she's just being friendly.