My advice is to adjust your expectations. You seem to expect that schedulers, including this team leader, will be considerate, reasonable, fair and/or interested in your priorities. Some may be, but others will simply look at you as a resource, a possible plug-in for a hole that's hard to fill. That's why and how this person did what she did.
I agree with others; as a PRN, the most useful response is, "Yes, I'm available," or, "Unfortunately, I am unavailable." Not sorry - you have nothing to apologize for. And when someone says you must come in, see above. No explanation or justification after the first time, if you even elect to give a reason then, which I don't recommend.
If you elect to meet with the director, I'd suggest you clarify with her if there is another response from you under the circumstances that would be more effective. In all likelihood she understands that schedulers sometimes exert more pressure than staff would like to get shifts filled. They get to ask. You get to say yes or no; those are the roles of the scheduler and the PRN.