Chtěla bych říct:

„Je mi hodně nepříjemné, že kadeřnice stříhá vlasy velmi rychle, ani ne za 10 minut nebo i méně.“ Můžu to říct takto? Hlavně si nejsem jista tou předložkou (by?, in?, within je asi nejlepší)

She is always cutting my hair within 10 minutes or less.

Já osobně bych řekl třeba in less than 10 mins.

hlasuju pro WITHIN
hooofiho „in less than…“ se mi ale taky líbí víc…

no to je pěkné Díky

She always cuts my hair in ten minutes or less.

You can't use present progressive here

Američanka: I wanted to say that it is annoying habit and I really don´t like it. I read in Destination B1 that I can do it this way.

Aha – so then:

I really don't like it when my hairdresser cuts my hair in less than ten minutes.

I really don't like that my hairdresser always cuts my hair in ten minutes or less.

I really don't think you can use present progressive though – it doesn't make any sense. :

maybe I didn´t use it correct, at least I forgot „!“ at the end of the sentence. I know this „annoying habits“ only from that book. Now I can see it isn´t often used 

Here is an example from that book:
My brother is always borrowing my CDs without asking!

or (from I don´t know from what
A: I have lost my pen again. (zase jsem ztratil klíče)
B: Not again! You´re always losing your pen! (naštvaně: ty je pořád ztrácíš)

edit: AH, I remembered Marek´s article: never 10 in this usage, only „ten“ 

I don't know about you Americans but I've heard ‚She is always doing that.‘ hundreds of times… It expresses discontent.

Sure, you can use it with other verbs…but in this specific case, with this specific verb, it doesn't work – „she is always cutting my hair in ten minutes or less“. I can't tell you why – it just sounds completely wrong. 

you put a seed in my head Thank you for your answers

A bug in your brain?

exactly.
Never mind, I hope the solution will appear in future suddenly and unexpectedly 

I thought that „seed“ is from UK and „bug“ from US