Is my future sister in law flirting with me, or am I reading too far into it?

Me and the sister in law get along really well, so much so that my fiance and her husband say that we're basically almost twins. We like a ton of the same things, we have a lot of the same mannerisms, and have a lot of the same drives in life. We essentially have more in common than I do with my finance and she does with her husband. This had led to some interesting dynamics including me and her having some pretty long conversations during the days (the 4 of us live together). We laugh a lot together and have a number of inside jokes. We essentially have great chemistry, and whenever we talk, we always lock direct eye contact the entire time.

So me, my fiance, and her sister went on vacation out of town earlier in the month to see family, her husband didn't come, he stayed back home. Well I noticed that a lot of times throughout this trip, she kept "bumping into me", like standing waiting in line, she'd slowly move over an inch or so until like her arm or should was against me at least for a minute and then she'd move somewhere else. This happened at least 5 times. Or when she walked by me, she'd always brush against me, not overtly, but very subtly (no one else does this). Then at home, I noticed she'd always sit pretty close to me... she'd have more room on her side of the couch to put more distance between us, but she'd always been close to me.

Finally, I noticed when she sat next to me, she'd always sit leaning away from me, but extend her foot on the couch and would brush it up against me, I'd move my hand so it would brush against her foot to see if she'd react, and she doesn't. She leaves it where it is for a few minutes. Last night, she laid out on the couch next to me and put her feet behind my back for a few minutes. I have a foot fetish and have checked out her feet a few times, so she may have noticed.

Does it sound like she may be flirting/teasing a little? And suggestions how to double check and see for sure? Or am I looking too far into it?
Is my future sister in law flirting with me, or am I reading too far into it?
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