Taking her shopping somewhere is a great idea, just try to do it when it is not too busy, and you should not have a problem. When you approach the register say that it is homework to buy something and work with money.
Have you tried having a yard sale, bake sale or lemonade stand with her. My 6 year old loves to play store at home. She gets it from being present in all the booths I do with my photo gifts and craft business. If you do a yard sale, bake sale, or lemonade stand the client will expect her to be slow, and will most likely be patient. She will be excited to learn it as she will be making money too! Try not to make it obvious that it is a lesson and she will retain the info longer.
Another way to deal with money is to incorporate her learning into Allowance. If she sees how the lesson applies in real life it may stick better. For example I give my kids allowances. I take them shopping and they spend quite a bit of time trying to follow their budget when selecting their purchase. They pay for their item at the register. Also, you can have her divide up her money into spending, savings, charity... Then have her count out how much is in each.
Also, we have a reward system her at our house. I have a 9 and 6 year old. I print out a weekly chart for this activity. Every time they wake up with a clean room and go to bed with a clean room they get a point. Every time they take a bath/shower without me asking another point, and when they get to bed on time another point. Every point they earn equals a dollar in our house. We don't use real money but you could, or toy money. We have family movie nights on weekends. The movies each cost $3, the snacks cost $2 each. Anytime during the week they can watch a half hour show on TV for $1, or play a half hour of a video game for a dollar. You could really mix this up to make it sink in, for example instead of using whole dollars break it down into a dime, penny, nickel, or quarter each. Have her fill in and track her own chart earnings and spending.
You could make a memory game for her with coins. Get some poster board. Cut it into 2 inch squares. Tape or hot glue a quarter, nickel, dime and penny each to a square. Now write the amount of the coins each on a square. place all the cards face down. Have her play the matching game. She will select a square and turn it over. If she turns over a square with a penny on it she has to find the written 1 cent (with cent sign) square to match it. If she does not seem interested play with her.
I have found that my kids learn the lesson better when they are doing it with me, and I am not forcing it. Make it fun and make it apply to real life. Good luck!