It's actually quite hard for a woman to do that, and not every woman can. I've been active for a couple of years now and have only done it once. Case and point- every woman is different, and just because she doesn't 'squirt' doesn't mean you aren't pleasing her.
She might mention the sensation that makes her feel like she's about to pee. It's very hard to distinguish between the actual feeling of urination and climax. If she mentions this, you should do your best to help her relax, because it's a very odd feeling. She may feel self-conscious and worry too much about 'accidentally peeing'. That anxiety can instantly oust the pleasure.
Did you think that all women could do it all the time? Is that why you're asking? Because it's highly uncommon for women to be able to do that at all. Only a small percentage of women are able to do it without even trying, and some can do it if they really make a huge effort. But MAJORITY of women can't do that. Did you really honestly believe that all women could do it all the time? That is just not true at all.
Agreed... many women DON'T squirt, so it's nothing to be alarmed about. In fact, many women AND males I know prefer that this doesn't happen, as it can be pretty messy. As long as you are both enjoying yourselves, that's all that matters!