Ah this was me. My now husband has three adult kids, two were warm (A&B) and welcoming, the other (C) was polite but as cold as ice. I even got on well with my partners ex wife (they parted many years before me).
I bent over backwards with presents and making time for them, only to be ignored and I decided that was a "them " problem and continued treating them as I hoped to be treated back. We had family holidays, we invited them all and they came. But still a cold front from C - I just decided that they didn't have to like me but I wasn't going to create an atmosphere so I continued being friendly. Year 5, me and partner married . We have been together for 15 years now.
Things have changed. I continued being nice to C and they continued to ignore me and their Dad. No cards, no visits, only texts when they needed large amounts of money (they earn more than us).
I learnt that it was costing me too much to maintain being nice as the continual rejection was really depressing. So I decided to match their mood, I stopped sending cards, presents and inviting them out and paying for stuff.
A & B are fully onboard with the situation and when C has made comments about having had no gifts from us, A&B have said to C that we understand how that feels because for years we sent cards, presents, invitations and money without any reciprocation or even acknowledgement and so we had decided to match their mood. I think they were shocked. We do now get occasional cards and an odd present, we have even had an invitation to their home and when this happens I reciprocate. Its very slow moving.
But here is your problem, you need your partner to come on board with this. It is his daughter and he needs to stand firm. He should never abandon her but he does need to put boundaries in place for an expectation of behaviours from her and you. And you need to set boundaries too. Your partner needs to buy her cards and presents, you back off. Issue invitations but don't push, make her welcome in your home but stop trying so hard. I have been there.