How to get milk supply back?

My daughter is 2 weeks and 5 days old, and I’m a first time mom. My in laws just came to visit for 4.5 days, and my mother in law would not let me hold or feed my baby the entire time they visited. Thank God they stayed in a hotel so I could still breastfeed at night, but she seriously held and fed my daughter for over 12 hours straight every day so she could “just memorize every little detail of her granddaughter” because my husband and I live across the country.

Anyway, they left at around noon today, and annoyances aside, I went from nearly exclusively breastfeeding and expressing roughly 9oz per feeding using a Haakaa, to getting a mild case of mastitis and expressing maybe 3oz max per feeding after my MIL bottle fed her for nearly 5 days straight.

Other than the obvious answer of just resuming breastfeeding, is there any way I can get my supply back?

(Side note: mastitis was taken care of two days ago by using Epsom salts/hot water in a Haakaa).