Magneto-intersubband resistance oscillations (MISOs) of highly mobile 2D electrons in symmetric GaAs quantum wells with two populated subbands are studied in magnetic fields B=(B⊥,B∥) tilted from the normal to the 2D electron layer at different temperatures T. The in-plane component (B∥) of the field B induces magnetic entanglement between subbands, leading to beating in oscillating density of states (DOS) and to MISO suppression. Model of the MISO suppression is proposed. Within the model, a comparison of MISO amplitude in the entangled and disentangled (B∥=0) 2D systems yields both difference frequency of DOS oscillations, df, and strength of the electron–electron interaction, described by parameter εF∗, in the 2D system. These properties are analyzed using two methods, yielding consistent but not identical results for both df and εF∗. The analysis reveals an additional angular dependent factor of MISO suppression. The factor is related to spin splitting of quantum levels in magnetic fields.