Before I went to the recommended extreme I would want to know a few things. What are her diapers like? As in, is she wetting frequently throughout the day? Is she happy or consistently fussy?
I would definitely want her to gain a little faster, but I would be very careful supplementing. It can start a very vicious cycle that can be hard to break.
Have you tried making lactation cookies? There was a post on those not long ago. They are delicious and can help your supply tremendously. And don't worry about eating cookies, you are feeding baby!!! Make sure you are drinking tons of water. Eat oatmeal, drink mothers milk tea, etc.
For right now, offer the breast frequently. I'd go every hour and a half if she will take it. And pump after feedings when you can.
Most importantly, follow your gut. Even at only five weeks you know your baby better than anyone. If you think she's hungry and not getting enough, add a bottle here and there. If you think she's a happy, healthy little girl who just doesn't gain fast then monitor and plug along. Just keep track and make sure she's gaining.
Good luck Mama!