There are a few theories floating around and you're right that the ability to remove the parasite should have gone as well. If you remember when she removes the parasite she releases enough energy to shatter the glass behind her. It may be that she has reached her limit, or that she has worn the power down and that it needs to replenish. There is also the theory that her powers are directly linked to the mindflayer and the upside down, with the gate now closed again (at least in Hawkins) it may be she no longer has the abilities.
Her powers are also directly linked to her emotions, her losing Hopper together with her using them a lot may have worn her out completely and they are lying dormant until she really needs them.