The Student Room Group
every girls reacts differently whilst being on the pill. me and my friend are both on the same brand but have totally differnt side effects. whilst i have lost weight, shes gained weight, her sex drives increased whilst mines the same etc etc. its more of a waiting game at the start, whilst her body gets used to it. plus theres always the option of changing her pill if it doesnt suit her etc.
Reply 2
Whatever happens, it may not happen immediately either - she won't turn into a screaming PMS monster overnight.

She may have no side effects, or she may have some. If she's not happy with them she can see her doctor and change pills.
No-one that I know has suffered any particularly noticeable side effects from the pill. My boobs got bigger, and one of my friends reckoned that it made her put on weight, but it wasn't anything major. None of us really feel much has changed sex-drive wise, so chances are if your girlfriend does get some effects, it won't be life-changing for either of you.
And if it does get bad, she can always change brands, so shouldn't be a problem!
have a look at this thread made it should give you all the known side affects http://www.thestudentroom.co.uk/showthread.php?t=79580