Im glad your mare has found an owner as lovely as you. I agree with the above message regarding the worms. As to your flatwork, the importance here is to do this correctly. 10 mins of good is worth more than 30 mins of bad training let it be groundwork or riding. You want to make sure your building up the right muscles eg. Lunging on a 20 metre circle:- a horse who has no rear end muscle will automatically pull him/her self with its front legs opposed to pushing him/herself with its back legs. You can see this as the back legs wont track up (the inside back foot will not step into or infront of the hoof mark made by the front foot). A similar thing can happen to his/her neck muscle just like us they will compansate and go for the easier option. Also just like us starting at the gym, they will ache so make sure you give them a day off too.
Always make sure you dont do more than 10 mins lunge on either side and always do both sides equally.
I know its about £70 but a well worth long term investment get a passoa it works all the muscles in a correct manner from head to tail.