Hmm...it's probably a good idea if you start slowly extending her wake time to around an hour and 15 or so (not much more). Some lo's simply need the extra sleep though, but usually at around 3 months they're up a little more than an hour. I think at 3.5 months mine was up to 1.5 hours, and that was pushing it a little bit.
They will resist, but if you're persistant (and consistant) enough they'll be able to stay up that long. 45 min naps are usually the result of a too long awake time or too short one. In your case I think it's too short. 30 mins is great for a newborn, but not necessarily for a 3 month old.
Hope this helps!
*HUGS*
Sonya =P