repeat??

booking 15 minute appointments tends to make you lose track of time in a hurry..i usually hate to bring stopwatches to my sessions..

That you were able to get through different positions in 15 minutes.

You said she was awesome, so if you really liked it and don't mind the super constricting time frame, then see her again. Simple, really.

I'm not sayin you don't but why call you later and tell you. The fact that you both went over is on BOTH of you. You knew how much the short was worth and if time goes over you pay up. That said if you really liked her than repeat but be sure that you leave on time or pay up.

...really bad form to me.  That would put an immediate damper on the mood of any future engagement for me.  I would choose to move on...  If time was going over, that should have been noted at the time.

Really it's up to her to keep track of time.  Providers must be excellent time managers & still keep  it discreet.  It's scam-ish for her to let you run over then demand more money.   I wouldn't even be surprised though it's not on my list of scams!  Normally over-time is on her unless you request it & agree to additional payment to extend.

OK, that said...  if you like the service...  and the rate for the time was what I'd expect to pay for that time / service...  I'd pay her & continue to see her.  If I care about seeing her again...  or her demands were unreasonable...  then I'd move on.  But I'd get very clear on what her rates are for an appropriate time interval.
I used to book hour & a half.  More recently it's been hour.  I wouldn't go less...  I'm not into quickies!

that called me back after a session would not be seen again by me. It seems very indiscreet to me....now if I set up another appointment and she brought it up that would be another story.

I personally feel that if I as a provider run over in time it is my own fault. I have run over and have never asked for more. Really strange that she called you after the fact as well, if she had an issue it should have been discussed before you left. Sounds like you had fun which is great but honestly her calling was a bit off.

They must be excellent time managers...  some use music tracks...  some just sense.  I noticed one Favorite lady...  the same little clock was always in our play area...  to the side.  Neither of us could see the bed side clock.  I figured out she was placing it.  
It's not right for her to let it run over THEN ask for more.  She should catch it at the time & say do you want to extend.  I have requested to extend & was glad I did.  But I learned "Specials" can be for lesser times or lesser services.  It's well to find out at the beginning.  
If she does not manage her time well...  then demands additional...  it would leave a sour taste with me.  If it happened once...  maybe she's new??  But she needs to learn to manage her time better.

No calls after the deed is done!

How? In 15 minutes? I've never had session that has lasted under a hour. I've lost track of time in a longer session. It was noticed before you left. You should have came to arrangements for additional fees then. Her calling you later asking for more funds is bullshit and I wouldn't see her again just because of that. Her pussy could have been made of gold but once the session is over and I have left you don't call me. I contact you in reference to future appointments. Calling and telling me later I owe you more sounds like she had a pissed off pimp. Stay away!