That's because she is saying 'Uilleam' not William! I agree with Joanne, there is nothing wrong with her pronunciations. I'm quite sure a fluent Gaelic speaker would be a tad annoyed if a learner is telling her she's not pronouncing her words correctly!
You ears adjust over time and I know it can be frustrating now hearts have been introduced to keep losing lives on a singular sentence.. put headphones in and listen to the sentence while it is written out infront of you and you will start to hear it clearer.
For the same question?
Uilleam is the nominative form - if you're talking about him then you use this one.
Uilleim is the vocative form - in the same way "balach" -> "a bhalaich", "Uilleam" gets slenderised by putting an 'i' before the final consonant and becomes "Uilleim". It doesn't get an "a" with lenition because it starts with a vowel.
I'm sorry, I didn't mean to offend with nominative/vocative. I mentioned that because you had two sentences here and I wanted to make sure "last time" wasn't referring to the "come inside, William" sentence.
I hope Joanne or Ciaran can get that sorted/answered for you!