If you really care about her and you can see that you've got stuck in a bit of a rut, book yourself a table somewhere nice and/or do something fun during the day. You probably need to inject some spark and if you want things to last then a bit of effort and surprise will show that she means something to you and that you're both just being stupid. You can tell her over dinner that what you said was a ridiculous mistake and tell her what she means to you, even with a letter, poem, anything. However, if you really can't see you lasting, then there's not much point and treat it as just another night in/out. It's your call, either grow a pair and sort **** out asap with some imagination and sensitivity, or leave things as they are and it'll fizzle out in no time at all. Best of luck if you go for the former.