Incall : She usually shower after you leave. You can take the last 10 mins yourself to shower before going or if you prefer showering home/etc and are ok to just leave "as it is" then you can use this time. The key for incall is to be outside the condo/app etc when your time is up.
Outcall : It depend on the agencies(some promise you the full 60mins with the client) but the standard is usually the last 10/5 mins are for the shower of the lady. I think it should just be played "nicely" personally. For instance if you are done and just talking/cuddling, personally im all fine she go in the shower at the 10 mins mark, usually they don't see a problem to keep talking if you had a conversation while they clean. But if you are on the verge of cumming and you know its only a min or 2 away and it looks like your really trying (fast masturbation etc) i would be very piss if her alarm start at the 10 min mark and she just get up and say "sorry times up, ill go take a shower". That would be VERY UNCOOL. This is basically where the "clock watcher" tag fits. But its important to note you should never go over your 60m tough. I kinda see that last 10 mins as a grace period, i mean if you don't need it, then cool she can prepare slowly and all, but if your still actively going at it (especially first sog) then i think its ok she eather cut her shower time a bit or take 5 more mins in your room to finish. This won't immensely delay the whole schedule.
And lets face it, most providers excuse themselves in the bathroom for 5m or so at the beginning of every encounters to "fresh up" so its not like she can't do it... In the case of incall/outcall agencies maybe her next client is an incall so she have more time to clean at her place/the agency place.
So basically yes in the perfect world you should be done by the 50 mins mark, and providers usually don't like when clients try to take 58 of the 60mins for sex entirely... But sometimes you can't help it, conversation is nice, you would think of yourself as being rude to cut it and say "well can we start plz?" so you go with the flow. But obviously you have to give yourself a limit. Here is my "barem of outcall"
Lets say she arrive at 6pm
6:00 to 6:05 : Her fresh up time
6:05 to 6:15 : Introductions and chit chatting
6:15 to 6:45 : 30 mins of nice sex
6:45 to 6:50 : Post sex talk
6:50 to 7:00 : Her clean up and dressing up time
By 6:20 if sex has not started tough, i have to make a move and start it, otherwise i may not be able to finish. But usually it mean conversation is good so chemistry is good and its easy to say it in a funny way that does not seem rude or anything.
Sometimes intros and fresh up combine last less than 5 mins, in that case it become longer post sex talks and sex is extended maybe by 5 mins.
Its weird i had girls who seem super shy at first, where i was thinking in my head "ok better make a move, this conversation is going nowhere" but then after we had sex she would feel more at ease and then it would turn in a nice conversation.
I got to be carefull myself. Im shy for initial contacts but if she is not shy too, i can turn into a chatterbox pretty quick. I just think its harder to ask questions as a client due to the obvious protective/secretive nature of SPs. But once she initiate the conversation, its easier. Always easier when she like video games, metal music or something currently relevant (like the latest marvel movie etc)
Cause otherwise i dunno what to talk of. I know nothing of clubs, DJs and all this stuff the young ladies like lol.
Anyway hope this message (or part of it) helps you. Obviously it would help us to know wich context you where in when she decided to go in the shower to say if it was apropriate or not.