What do you do if a person in your group purposely misleads you?
Unfortunately it happens, not just in undergraduate research. 

What you should or could do strongly depends on your evidence and the perceptions of other people involved, here supervisors. However, assume you are right and you have evidence, still then supervisors often do not like to hear you complaining about someone they like or value. You will not change their minds easily.

So my advise would be to follow what you expressed already. Just perform well independently. But also make sure that your work and effort is visible. You may need to step out of your comfort zone and be more extrovert and assertive. If you do not occupy your space, others will. 

You can see this as an excellent learning opportunity to improve these skills. Try to park the negative emotion for now if it does not help. Do not deny it but promise yourself to assess it later. Experiment with different behaviour and approaches and consider it as a training in personal leadership. After the summer make a list with behaviour you considered effective and less effective. 

Wish you all the best.