Well, i just had my fourth little girl and she is now the same age as yours. some babies seemingly cry "all the time", and others just when they really need something. hang in there if she cries a lot. i can deal with crying so much better now than i did with my first... i couldn't stand her crying for more than 10 min at a time. she habitually cried every time before she fell asleep (my first), and i made the mistake of picking her up or rocking her all the time when she actually needed practice calming herself down before she slept... needless to say she is the one that gives us the most "sleep problems" now @ 5 years old. we learned with the next three, and they are WAAAY happier sleepers- they ALL (even the three month old) sleep a good 11 hours a night.
of course crying isn't all about sleepy time... you WILL know the difference in her cry if something is actually hurting her (i.e. gas, she's scared, hunger, too hot/cold, etc...), or she's just being a but fussy. either way, babies go through a GAZILLION stages...
so hang in there, and just let her know that you are there for her even if she is being annoying. seriously. babies know if you are stressed out, and they NEED to know that you will be there no matter what, so just let her know that all is okay, and if she cries, she cries.
Babies LOOOVE baby slings (properly used), so if all else fails and you are going nuts, try it:)