My two factors were - match with PJ but more important match (and good flow to) your last name.
I like these names but I don’t think they go with your last name: Summer, Billie, Clementine/Lemmie, Frankie, or Esme - all too much of a mouthful and/or too fast paced.
I went for Lucille as the pace goes so well with last name. I think Lucky is so sweet and I also like the simple and elegant, Lil.
I also really like Murphy - but with a very feminine middle to balance.
Matilda is good but I think Tilda goes better than Tillie with last name (though obv flow from a nickname not as important).
Also, if want Clementine (still think tricky with last name) then Cleo as a nn or even Minnie - obv Minnie rhymes but still easier than Lemmie with last name (though see above re nicknames).
I’d also suggest Bridget nn Birdie, or Willamina nn Billie, so both have a long & “proper” name. Same for Frankie - would use Frances or Francesca so broadly equitable - I wouldn’t want to be Ozzy or Stevie or a nickname name if my sister were Penelope (and I think Ozzy and Stevie won’t age well as full first names). I prefer Francy or Franny to Frankie (it’s quite harsh incl with your last name) but obv take or leave, as with all.
Other options:
Josephine - Josie
Cecily - Cessie, Cece
Eloise - Lola, Lulu, Elle, Lois
Florence - Florrie, Flo, Ren
Margot - Mimi (two M name)
Beatrice - nn Birdie - flows more smoothly imo to MacK.