No, I haven't been told that I socialise well, but once someone told me that I was diplomatic. It was a school friend that I hadn't seen for a long time. She asked me, "have I changed?" I thought about it a bit and said, "yes and no." She said, "oooh, that's diplomatic!" Thing is, I wasn't being deliberately diplomatic, I was being honest and accurate. Physically she has changed, but in terms of personality, no. And she still loves cats just as much as she used to.
Adults with ASD can learn social skills as they get older and gain more life experience, they learn to mask, or learn scripts, or dos and don'ts, in common social situations. So it might not be until you get to know them a bit better that their ASD becomes apparent, and this is especially true of females, which is why they go under the radar and their ASD is often either misdiagnosed or just doesn't get picked up on. So it is possible that someone with ASD may have good social skills - they learned them, but when they are in a new or unexpected situation, they may not know how to deal with it, lacking the natural intuition and instinct, and then appear socially awkward.
Your mum knows you a lot better than an online test, or your therapist, ever can.