Maybe if I just remind you of a couple basic, foundational elements of multi-relationships it may help you keep some perspective. In the meantime I suggest you continue to do lots of reading and talking to experienced people.
So here goes.............
1> The connections we form with different people are ALL different in nature. It's always a trap to fall into a 'more' or 'less' comparison. It just isn't that way.
That fact that you and he may have (initially) connected more deeply on some basis or another has nothing to do with the connection you form with her.
And maybe more importantly, ALL this is subject to change in the future. It could completely flip-flop over time ! So if you intend to navigate multi-relationships you need to develop a skill of just letting this flow and accepting them as they are - at the MOMENT !
2> A similar concept is going to apply to time. If you continue you will be sharing time as well as emotion. Time is finite. There WILL be times where conflicts occur, someone may be inclined to feel slighted etc. Get used to it, and practice building solid, non-confrontational communication skills so you can work through it without it wreaking havoc unnecessarily. Try to learn to ALL seek balance - NOT equality ! There is a difference
If you work as a team and don't allow some competitive wall to grow between you and her then it's quite likely your bond will grow deeper - if in a totally different (and maybe surprising) direction. Keep an open mind and try to be flexible
As the old lyrics wisely said...........
"We don't always get what we want - but if we TRY - sometimes we get what we need"
Good luck and stay tuned.