OK I get it, I've had two Labs, my current one turns 8 in May. A really cold winter like this sucks for walking a dog like a Lab as it's been so damn cold. Dress in layers so that your good and warm and try to get at least a brisk half hour walk in three times a day, keep plenty of small broken up treats in your pocket that you can get to quickly and of course baggies to pickup after them. Keep her leash in both hands; the loop in one hand and give her very little room to move from your side using your other hand but keep consistent control over her except when she goes to the bathroom. When she successfully walks along side of you for a period of time praise her and offer her up a small treat to reinforce that she's doing good. Labs are eager to please and learn real quick, treats reinforce good behavior - keep on it. Your also going through what sounds like the "terrible 2's" (with Labs, from about 1 year old 'til they're about 3) so be patient but firm. Your the boss or the "pack leader" as Cesar Millan would say, not her, so make sure she knows it. It goes without saying, never hit a dog (NOT saying you would ever do that!), they don't know why they are being hurt and distrust can set in quickly. With Labs the first 3 years can be a fair amount of work but let me tell you, you'll get 9 maybe 10 years of the best dog in the world after that and you'll be willing to do it all over again when you see what amazing dogs they are as they enter adulthood. If she's not spade get it done now unless you plan on breeding her. That helps settle dogs down a bit.
Don't get a second dog. That's double trouble, trust me, I've been there.
