Tongue tie breastfeeding help

Does anyone have any tips to help carry on breastfeeding with a tongue tie? She has the division booked for 2nd April but I'm starting to lose hope with breastfeeding. We're currently bottle feeding (breastmilk and formula) but I try to latch her on once/twice a day. However, whenever she is latched on, she ends up sleeping most of the time. I've tried everything from tickling, blowing, nappy change, laying her down etc but nothing seems to work. Any advice?