Honestly, at 2 months, I was still in survival mode. I followed cues (or tried to) & tried to keep the order right for the most part (eat then play THEN sleep). I don't know of a correlation between 45 min naps & bfing.
You look for a few things to make sure they're getting enough while bf'ing:
1) enough wet diapers?
2) gaining weight appropriately?
3) satisfied after a feed? (i.e. not rooting around or crying for more)
If yes to all that, then your supply is OK. If not, there are some thing you can do. Try the double-side feeding for a while. Compressions help. See if you notice a difference. It's possible she's hitting a growth spurt & feeding often/wanting more is her way of boosting your supply. There are also herbal supplements and even pharmaceuticals to help boost supply, if it comes to that.
If you want to continue to bf, I would be very hesitant to suggest a formula top-up. Bf is all about the laws of supply & demand. If there is no demand (i.e. no baby on boob) then the supply drops. Then you need more top-ups, which leads to less demand & less supply. If weight is an issue & you need to do something *now* there is something called a Supplemental Nursing System (SNS) that both allows the baby to get a supplement (EBM or formula) while nursing at the boob so you both get what you need.
Pumping is good for having breast milk when you're not there, but pumping is not an indicator of your supply. It only indicates how well you respond to a pump. There are all sorts of physical & hormonal things that go on between mother/child that don't happen with mother/pump. It is entirely possible for your supply to be fine but hardly pump anything. Similar for length of time... Each child is different. My J was a leisurely nurser (15-20 per side!). When Isaac came along & was done with both sides in that same time, I thought something was wrong. But no. He was just a speed nurser.
I hesitate to give nap/sleep advice (not my forte), but I know that sleep is developmental (stretching into longer segments). It does seem as though she may not be getting enough sleep.
http://babywhispererforums.com/index.php?topic=85130.0 15 hr seems to be on the low end of "normal" for her age, but if you say she's OT, then she needs more. Have you posed on the naps board? (Sorry if I'm stating the obvious.)
Sorry for the epistle. Hope something in that helps you.