Hywel's inclusion forces Elen Evans back to centre with Rebecca de Filippo dropping down to the bench while captain Rachel Taylor switches from second row to back row with Catrina Nicholas moving to the subs bench.
Both teams are yet to secure their first win of the campaign but Edwards is confident Wales can claim their first win in front of a big crowd on Sunday.
"We know we have been improving in certain areas during the campaign," he said. "It's a case of putting all the good areas from all four games into one game - if we do that we should put Scotland to bed quite early."
With one eye on the World Cup later this year, Edwards said he made the changes to give some players game time and an opportunity to stake a claim for the tournament.
"Sian was a squad player last year where she didn't get any game time - this year she has been an able understudy for Amy Day who I think has had a really good tournament , probably one of her best for a couple of years. Amy hasn't done anything to be dropped but this game gives Sian a chance to go out and prove she can start with tempo.
"We also looked at the forwards and now have competition for places. We were conscious not to change things too much - we're blessed with the calibre of players we have so it's all about getting the right combinations."
Wales Women v Scotland Women, Sun 16 March, Talbot Athletic Ground, 2pm
15 Dyddgu Hywel (Bristol Ladies)
14 Ffion Bowen (Maesteg Celtic)
13 Elen Evans (Waterloo)
12 Robyn Wilkins (Llandaff North)
11 Philippa Tuttiett (Bristol Ladies)
10 Elinor Snowsill (Bristol Ladies)
9 Sian Moore (Bristol Ladies);
1 Jenny Davies (Waterloo)
2 Lowri Harries (Neath Athletic)
3 Catrin Edwards (Bristol Ladies)
4 Jenny Hawkins (Llandaff North)
5 Shona Powell Hughes (Neath Athletic)
6 Rachel Taylor (Capt) (Bristol Ladies)
7 Nia Davies (Cardiff Met)
8 Sioned Harries (Llandaff North)
16 Carys Phillips (Bristol Ladies)
17 Megan York (Blaenau Gwent)
18 Caryl Thomas (Bath Ladies)
19 Catrina Nicholas (Llandaff North)
20 Sian Williams (Worcester)
21 Amy Day (Llandaff North)
22 Rebecca de Filippo (Bristol Ladies)
23 Laurie Harries (Llandaff North)