diff --git a/dimelo/plot_read_browser.py b/dimelo/plot_read_browser.py
index a49d496..febccac 100644
--- a/dimelo/plot_read_browser.py
+++ b/dimelo/plot_read_browser.py
@@ -342,13 +342,17 @@ def make_browser_figure(
         colorscales: dictionary mapping motif names to plotly colorscale specifications
 
     TODO: Think about how this interfaces with different types of initial sorting...
-    TODO: Make it so that this method does NOT modify the input dataframe
     TODO: Should this method do the collapsing, or should this method require collapsing outside?
     """
     if collapse:
         index_map = collapse_rows(read_extent_df, **kwargs)
-        read_extent_df["y_index"] = read_extent_df["y_index"].map(index_map)
-        mod_event_df["y_index"] = mod_event_df["y_index"].map(index_map)
+        # NOTE: `DataFrame.assign` performs a deep copy, preventing the modification of the array that is passed in. For very large datasets, this duplication may cause memory issues.
+        read_extent_df = read_extent_df.assign(
+            y_index=read_extent_df["y_index"].map(index_map)
+        )
+        mod_event_df = mod_event_df.assign(
+            y_index=mod_event_df["y_index"].map(index_map)
+        )
 
     # Build final figure
     # TODO: Enable setting some relevant parameters