I open Q9o in the CO and only the BB calls.

234...She checks, I check

2345...She checks, I check.

23452...She bets.

The fact that she hasn't donked the flop or bet the turn means she has nothing(trust me). She doesn't do much CRing. She will bluff in this situation 100% of the time. The pot is tiny. She could accidentally value own me. Is this a spot to raise to make sure I don't get owned? She doesn't hand read so I wouldn't fear her 3 bet bluffing me. Or should I just move on and wait for a spot where I have a stronger high cards like K high? I think she would intuitively realize that she didn't need to bluff her K highs. She would 3 bet pre flop with her better K highs.

I feel like there is easy money to be had here. Perhaps I've spent too much time on a 3.5 big bet pot.

In conclusion the question is how how low can I go regarding just calling. Also, Would you consider raising any non show downable hand here?

You answered your own question. She has nothing, but might accidentally value bet you with a better Q or K hi. So just bluff raise everything including your Q9. Why would you do anything else? Calling is terrible based on your read.

You can raise down to like K9 or whatever you think her strongest king is. You're taking down the pot 100% of the time, right?

What value hands do you check twice and then raise?

I prefer a flop bet here.

I am never checking a value hand twice. I am fully aware that we have 100% bluffs here. But villain has nothing 100% of the time and is bluffing 100% of the time and will fold anyway based on OP's read. Exploitative play is a thing.

+1

As played, folding isn't terrible and flat calling is the worst.

Bluff raising is effective if she only plays her hand and/or is unable/unwilling to call down this type of board with K high even if she is able to reason that you don't have any aces due to your check back on the turn; most other players would ask the same question regarding your line, especially checking back turn when you have more aces in your late position opening range than she does in BB defense range.

She has a more 6's in her range than you do as well as more 2's, 3's, 4's, AND 5's which if she didn't bet the flop she could/should now bet the turn for for value as well as some bluffs, where you can only be betting an ace for value and have near zero 2-6's as bluffs. Same goes for river.

Against an opponent who not only is breathing and has a pulse but can also play a little poker, they would/should be apt to re-raise you on the river with almost certainty that you have value-owned yourself with absolute air.

I think it's too much headache for the pot size in addition to unknown reaction by humans as they are the most unpredictable lot.

Fold why waste your rake over this?

seems like the best play is to bluff raise, but in real time id just muck without thinking.

are you sure she has nothing? Ax plays this way a lot trying to induce you to bluff the turn.

You are repping turn slowplay? Lol

Did you miss the "she doesn't hand read" part?

Imo the better play is to just bet the turn if your reads are correct. Wouldn’t she just lead if she had a straight? after all your read that she has nothing is contingent upon the turn play.

even checking it down when she has 9 high seems ambitious, since your read is that she is too aggressive in weird spots.

I would always raise here because like you said she has nothing, but better play would be raising on flop.