Search Results: how long should i wait

So this is a pretty long story. The reason I need this much advice is because I'm a chronic overthinker and have gotten hurt by misinterpreting "signs" I thought I was certain about.

My [M21] friend [F25] and I are mutual friends of my cousin [F30]. Three of us have been hanging out every weekend for the past four months. Girl has been to a family wedding, events, parties, etc. The cousin has told other cousins (who want the girl and I to date) that she doesn't want to lose a friend, but it's more that she's 30, hasn't had a boyfriend in years, plays around with guys, and just wants a sidekick to go through it with.

The girl started being very flirty at end of May. She has:
- Told me I have pretty eyes
- Major physical contact: grabbing my hand, resting her head on my shoulder (especially when I make her laugh), hugged me from behind, rubbed her whole body up against me
- Jokes or "jokes" with my parents being her in-laws
- Sent me a picture of a hot bathing suit for opinion on color
- Sent me a private snap of her in a sports bra and leggings before hitting the gym. She never private Snaps me.
- Has said "should we kiss?" a few times. Joking, but the last time was more subtle and serious.

Things didn't get heated until I started giving serious vibes back. The girl has said to a mutual friend, who's sort of my wingman, that I'm the "type of guy you marry, and take it slow with." I feel the same way about her. I don't to start something serious if someone else sees it as a game or just me being spiteful.

The problem is: some weeks the vibes are incredibly flirty and almost romantic, other weeks we're basically just friends. I can't really gauge what she wants and I want to make a move and escalate things but don't want to make her uncomfortable if she's not feeling it. Am I being "reeled in?"

Also, should I talk to my cousin first and state my intentions clearly, or should I wait until things sort of boil over, ending up in a serious moment or conversation?