An RNA:DNA hybrid is generally more thermodynamically stable than the same DNA:DNA sequence, but in your case the RNA is only 8 nt long. Such short hybrids have relatively low melting temperatures (often ~20–30 °C depending on GC content and ionic strength). If your complementary ssDNA is long (≈100 nt) and fully matches the DNA strand, it could in principle displace the RNA, but under physiological conditions and without enzymes (like RNase H or a helicase) this displacement would be slow and inefficient. At temperatures near or above the Tₘ of the RNA:DNA segment, or in the presence of RNase H, the RNA will dissociate more readily and the ssDNA can anneal efficiently.

Thank you, this insight is very helpful for my experimental design!