My mom got married somewhat later in life (still in her twenties, but very late twenties). Some of my favorite childhood memories are about her best friend- she used to babysit us, come to us for Shabbos, do our nails, go on Girls Night Out vacations with us, teach us how to swim, and just be an all-around amazing friend to both my mom and her kids. It was after SHE got married that we started getting together less. Now I babysit for her kids.
It really can be done. It must be so hard for you not to be able to have a friendship like that- remember, your friends are losing out too, missing a fantastic friendship with a fantastic friend :).