I definitely understand this! My first is 9 and my little is 3 months...I think it didnt really click for me until I had time alone with the new baby- thankfully for us that happened really early but if it hadn't I could definitely see still feeling that way!
I felt this so much in the first couple of days!! After my 1 year old goes to sleep with dad, I stay up with my little girl. Even if she’s just sleeping 🥰 that 1on1 time where she gets my undivided attention makes me feel less guilty. It’s actually the opposite now! I never have 1on1 time with my son now and he’s SUCH a mamas boy. He’s always touching me or holding on to me wherever he can it makes me so sad
I had the same issue bonding with my second. I don't know if your first is in school or someone is able to watch just her. I took a baby music class with just my second. It was nice to have that time just with him. I also spent like three nights in a row with just him at night while my first slept with my husband. That bonded us too.