Well, if she already suggest another event with her friends, it's better to accept.
During the encounter, you can create a lot of opportunities to be alone with her to make the first move and kiss her:
- call her to get a drink.
- call her to take a "air" outside of the bar (if the local has this kind of possibility).
- offer a drive to her home. When the car stop and you say goodbye to her, it's a good moment for a kiss.
- maybe her friends also help you and create some opportunity to be alone with her. But you can't count with that.
There is the possibility that everything goes wrong and the night finish with no kiss. It's very frustrating, because there is this expectation. If this happens, I suggest to you immediately send a nice message to her talking about how good the night was and that you are already waiting for a new encounter, but only with you two. This kind of message reinforce that you really like her.
Decline this invite, saying that you would like to be alone with her, could pass a bad message to her, because she doesn't know you very well yet.
Maybe she only did this invite because you not invite her for anything after the first encounter. Pay attention on this signals. If you think that was the case, invite her for a particular encounter could be her desire too. If you think that was the case, just suggest another alternative:
"hey! Can I suggest to you another plan for the weekend? :). Of course, if your friends are counting on your presence there, we can keep the original plan ;). I know a very good bar and blabla...".
This indirectly says that you want a encounter with you two only and create a "escape" to her decline this invite without be harsh.